View Full Version : Sansui Frequently asked, and more...


Pages : [1] 2 3

Morden2004
02-01-2006, 11:42 AM
This thread will be a [F]requently [A]sked [Q]uestions repository of information everyone wants to read. As time goes by, I'll be adding links here to (mostly) Exclusively Sansui threads where questions of great importance are answered.

If you find a thread that you think is worthy of being in our FAQ, just PM me with the link and I'll check it out.

And, BTW, private messaging any AK member is easy if you are reading one of their messages! Just click on the screen (AK) name at the top left of the message and select [Send Private Message].

Paul

Moderator - Exclusively Sansui forum

Morden2004
02-01-2006, 11:45 AM
The Exclusively Sansui FAQ List


FAQ 1
Can I make a new cabinet for my Sansui?
Here's a good one for cabinet making.
http://audiokarma.org/forums/showthread.php?t=54070
FAQ 2
What are fusible resistors?
No Sansui FAQ list could be without mention of fusible resistors
http://audiokarma.org/forums/showthread.php?t=47170
FAQ 3
How do I fix an intermittent 'Separated/Connect' switch?
All about the problematic connected/seperated switch on the big G.
http://audiokarma.org/forums/showthread.php?t=50077
FAQ 4
I need bulbs? (Part 1)
Bulbs and lamps. This only one. Maybe someone could recommend more.
http://audiokarma.org/forums/showthread.php?t=51405
See: FAQ 13 below for more bulb information.
FAQ 5
My Sansui is blowing fuses when powered up. What shoud I do?
http://audiokarma.org/forums/showthread.php?t=55659
FAQ 6
My Sansui is staying in protection mode. Why?
Protection fault
http://audiokarma.org/forums/showthread.php?t=26786
FAQ 7
How do I fix the dial lamp on my 9090/9090DB?
9090 Dial Lamp
http://audiokarma.org/forums/showthread.php?t=51901
FAQ 8
What is DC-Offset and why should I care?
EW's DC offset and bias thread (#1 in everyone's book) ...
http://audiokarma.org/forums/showthread.php?t=5634&highlight=offset
FAQ 9
Are replacement transistors safe?
Identifying counterfeit output transistors and using OnSemi MJ21193/MJ21194 instead of the originals.
http://Audiokarma.org/forums/showthread.php?t=53323&highlight=mj21194[/QUOTE]
FAQ 10
I have scratchy controls and a noisy volume control. What to do?
Cleaning switches and potentiometers {The Morden2004 method}
Cleaning Controls (http://audiokarma.org/forums/showpost.php?p=157699&postcount=15)



<Keep going down - more FAQ's on subsequent messages>

Morden2004
02-27-2006, 08:33 AM
Lights out in an 8080/9090? Here is a repair tip that will remove the light circuit from the selector switch which often fails.

"With the top cover removed, looking down on the right side, there is a pc board about 4" x 5 " that the selector switch is mounted on. On that board there are connection plugs. Second from the right there is a connector with a orange, grey, black and red wire attached. There is an open location on that connector. Move the red wire(~6.5 vac) from the end position to the vacant position next to the black wire. This new position will tap into the 6.5 vac supply that the source selector uses. Now the tuning lights will be on all the time and the orange source lights will switch on and off as the function selector changes(am,fm,phono,aux,dolby fm)

http://audiokarma.org/forums/attachment.php?attachmentid=397

More FAQ's below. Keep going!

Morden2004
03-15-2006, 01:04 PM
FAQ 12
How do I sell my surplus gear here on AudioKarma?
Subscribe, then use the Bartertown forum.
FAQ 13
Where can I get replacement lamps for my classic Sansui? (Part 2)
AudioKarma member Dave Wojo (dgwojo) has a great site for ordering bulbs. Click this link: dgwojo (http://home.earthlink.net/~dwojo/index.html)
AudioKarma member Denis (dhenryp) also sells lamps for classic Sansui gear. Check out eBay member ID 'dhenryp' on eBay

or contact either member using AudioKarma email.
FAQ 14
I have heard about the problems with glue on component boards. How do I get rid of it?
Click the link below.
Sansui glue (http://audiokarma.org/forums/showthread.php?t=63404)


<More FAQ's soon>

Morden2004
05-31-2006, 02:54 PM
FAQ 15: How do I tell what year my Sansui equipment was manufactured?

Easy! The serial numbers on most Sansui equipment follows a standard;

FF Y MM ####

where FF = a Factory Assembly Line number
Y = last digit of the year of manufacture (you need to know the first year a unit was built - see the Sansui Database reports)
MM = the month of build where 01 = January and 12 = December

The remaining 3 or 4 digits are sequentially applied on the line in sequence.

Example:

AU-999 Serial Number is: 222010985

Manufacturing line #: 22
Year: 1972 (first year for the AU-999 was 1969)
Month: January
Serial component: 0985

Morden2004
07-03-2006, 10:00 AM
FAQ 16: What does the Connected/Separated switch on my Sansui xxxx do?

Read this excellent explanation by our very own EchoWars here (http://audiokarma.org/forums/showpost.php?p=734059&postcount=3) .


FAQ 17: What is a 'Poor Mans Variac' and how do I build one?
Read this thread for an explanation of the PMV here (http://audiokarma.org/forums/showthread.php?t=41523&highlight=poor+mans+variac) .


And here are the construction pictures of my PMV. I think these are self-explanatory.
http://www.clarkeworks.com/images/AK/~PMV{1}.jpg

http://www.clarkeworks.com/images/AK/~PMV{2}.jpg

http://www.clarkeworks.com/images/AK/~PMV{3}.jpg

http://www.clarkeworks.com/images/AK/~PMV{4}.jpg

http://www.clarkeworks.com/images/AK/~PMV{5}.jpg

LBPete
02-24-2007, 12:54 AM
Many Sansui and other brands used clear Acrylic for the ďglassĒ on receiver and tuner dials. Acrylic is great for this purpose but can be scratched. Fortunately, Acrylic is an easily ďworkedĒ material and most scratches can be polished out. Sansui back painted the lettering on these dial faces so the exterior surface can be buffed without risk of damaging the lettering. Here is the faceplate from a 9090DB with several fairly deep scratches.

The process takes a little time but is well worth the effort. For deep scratches like these Itís best to remove the acrylic from the faceplate. That way you donít have to worry about accidentally damaging the finish on the faceplate itself.

The bezel is held on with screws and the acrylic is held in place with double sided tape. Try to keep the tape adhered to the faceplate as you pull the acrylic away. Also be careful not to tear the tape. You can usually reuse it. As a side note, Iíve seen a number of posts where people mention that this bezel is plastic. Itís definitely metal, probably a zinc alloy commonly called pot metal.

LBPete
02-24-2007, 12:58 AM
Scratches are cuts into the acrylic. You canít actually remove the scratch but you can remove the material around the scratch with sandpaper to lower the surrounding area to the depth of the scratch. Usually 400 grit wet/dry paper is a good place to start. If the scratches are very deep, try starting with 320 grit. The courser the sandpaper you use, the more work it will take to clean it up later.

Keep a tub of water handy and back the sandpaper with some dense foam. Wet sand the area around the scratches until you can no longer see them. Keep the sandpaper wet while you do this.

Repeat the process with 600 grit and then finish it off with 1200 grit widening the area. This will remove the fine scratches from the coarser sand paper.

LBPete
02-24-2007, 12:59 AM
Next comes the buffing wheel. It is a cloth wheel. These can be mounted in a conventional drill but itís a lot easier if you have a drill press. They can also be mounted in a dedicated motor like a bench grinder.

The cloth wheel actually heats up the surface of the acrylic with friction. You need to keep the acrylic moving or it can overheat and scuff. This takes a little time. To speed the process a compound like tripoli can be rubbed on the wheel. This increases the ďcuttingĒ action. Donít over do it or you can scuff up the surface rather than polish it. Also in some cases, it may be necessary to retouch the area with the 1200 grit sand paper if there are a lot of light scratches left over from the coarser grits.

LBPete
02-24-2007, 01:02 AM
When done, the Acrylic is bright, very shiny and scratch free.

The aluminum of the faceplate is polished with a metal polish like Semichrome polish.

And the finished product is ready to rock.

- Pete

kcollins4
02-24-2007, 02:20 AM
Really nice work there Pete!

alexkerhead
02-24-2007, 02:29 AM
Thanks for the guide Pete!

ZebraBlvd
02-24-2007, 06:33 AM
Very nice work Pete. Thanks for taking the time to post this polishing process. I for one will greatly benefit from it.

influx
02-24-2007, 07:03 AM
I and my G8000 thank you!

LBPete
03-09-2007, 02:42 AM
The unique feature of the 9090DB and itís little brother, the 8080DB is their ability to encode Dolby noise reduction. Dolby was very new in 1977 when these units were introduced. Most tape decks didnít have it. So Sansui provided circuitry in these receivers to allow it to add Dolby noise reduction through the tape output. These units can also receive and decode Dolby FM, a stillborn format. To calibrate the Dolby level, a test tone is built in.

Checking this tone is a simple test of the Dolby board. When activated by pushing the Meter cal/tone switch and choosing Rec 1 or 2 on the Dolby switch, you should hear a 1,000 Hz tone from both channels. In this mode the power meters are used for Dolby Calibration. In this test they should both come up to mid range.

The heart of the Dolby board is a 5 gang rotary switch. Like all switches in this vintage equipment, it is prone to oxidation. Since all audio signals must pass through this switch, it can cause symptoms like dropped or distorted channels.

The Dolby circuit board was very high tech in its day. I was one of the first PC boards used by Sansui to have circuit traces on both sides of the board. To connect circuits from one side of the board to the other, they pass trough holes in the board that are filled with solder. There are 64 pass throughs on the Dolby board. The electrical conductivity of these ďpass throughsĒ can fail causing dropped or distorted channels and or failure of one or more of the Dolby functions.

At some point in the production of these models, Sansui recognized the shortcomings of the pass throughs and installed rivets in them. Boards with these rivets should be much less prone to pass through failure.

The Dolby board is wired to a gang of push switches. There are a total of 36 wires that run from the Dolby Board to the push switch assembly. Early production models used another ďhigh techĒ innovation of the day, flexible PC boards to connect the Dolby board to the push switch assembly. These flex PC boards get very brittle over time and have a tendency to tear. If that occurs they cannot be repaired and must be replaced. Sansui identified this problem too. In latter production units, the flex PC boards were replaced by Ribbon cable.

The picture below are mid and late production Dolby and push switch boards. Both of these boards have riveted pass throughs. The mid production board has the Flex PC board and the late production board has the ribbon cable.

LBPete
03-09-2007, 02:44 AM
Iíve been restoring an 8080DB. The unit had typical Dolby problems. The test tone, Dolby meter and Dolby FM only worked on the right side. Thoroughly cleaning the Dolby and push switches did not bring it back. The problem was likely caused by faulty pass throughs.

An overhaul of the Dolby board is a daunting task, not to be taken lightly. Hundreds of solder joints need to be redone. There is a lot of opportunity for error.

The overhaul has 4 stages.

 Fix the pass throughs,
 Service the Dolby and push switches
 Replace the flex PC boards
 Replace all the electrolytic capacitors.

To do this work you need to have a desoldering iron. I use an $11 Radio Shack desoldering iron. It works like magic. It is also a good idea to have an adjustable soldering iron. It allows you to turn the heat up or down as needed. I use a Weller WLC 100. Itís also helpful to have a digital camera handy to take pictures of component and wire locations.

Since the flex PC boards are going to be replaced, unsolder them from the Dolby board first. This will make it a lot easier to remove the board. The push switch assembly can stay in place for the time being. Be sure to make note of the position of the yellow and black wire that need to be unsoldered from the Dolby board to remove it.

LBPete
03-09-2007, 02:48 AM
The easiest way to get the Dolby and Push switch boards out of the chassis, is to remove the four screws that hold the front rail of the chassis and separate it slightly from the side rails. This give you more room to pull the boards out.

There are a number of pass troughs under the Dolby switch. To get to them, the switch should be removed. Here is the switch being unsoldered. Make note of the position of the 4 small capacitors. You will reinstall them later. (As a side note CDFixer mentioned that these caps were eliminated in later production so it may not be necessary to reinstall them.)

About halfway through removing this switch my hand started cramping up from working the vacuum bulb on the cheapy desoldering iron.

Itís a lot easier to clean the switch when it is sitting on the bench. You can use a contact cleaner on it and then follow up with Deoxit and Pro gold. Be very careful to clean all the solder pads. Residue from Deoxit might cause solder not to bond properly when you solder it back in.

Also be sure to clean the push switches. Line up the application straw on the Deoxit can with the last hole in the top of the push switch. Hold it flush against the hole and spray. This should force the cleaner into the switch. Then work the switches at least 10 times. Move the straw to the first hole and spray again. Cycle the switches again. The red arrows point to the holes.

LBPete
03-09-2007, 02:51 AM
With the Dolby switch off the board, you can see how complex the circuit is on this board. The screen printing on the top side shows the traces on the opposite side of the board. You can also clearly see the green electrical traces on this side of the board.

The best way to permanently improve the conductivity of the pass throughs is to insert a wire into the hole and solder it on both sides. But before you can do that, you need to remove the old solder. Here is the board with the solder cleaned out of many of the pass throughs. You can see the rivets in the holes. There are also pass through peppered in with all the components on the right side of the board. You need to look very carefully to find them all.

Once the solder is cleaned off of all the pass throughs, itís time to start pinning. The cut leads from electrolytic capacitors make great stock for the pins. These leads are tinned to make soldering easy. Bend the lead over on both sides. Many of the pass troughs are in tight quarters so be very careful that the bent over leads donít contact adjacent components or traces.

Solder each pin on both sides of the board. When heated with the soldering iron, the rivets help the solder to flow freely to the other side.

Next itís time to replace the electrolytic caps. There are about 25 of them on this little board. Do them one at a time so you match the polarity when you install them. Hereís the board with a set of fresh Panasonic FCs. They are a lot smaller than the originals.

LBPete
03-09-2007, 02:56 AM
Next the Dolby switch can be reinstalled. Pay attention to the location of the little caps that were removed earlier.

Before installing the new ribbon cable, the flex PC board must be removed from the push switch assembly. Be very careful when unsoldering the flex PC board from the push switch. The solder pads are tiny and lift very easily. Be sure to get all the solder off the pins before trying to pull them out of the board. Several of them lifted when I was taking this one off. After installing the ribbon cable, I reinforced them by running a wire parallel from the cable to a solder point down stream.

Now the new ribbon cable can be installed. It is available from Digikey. Get the 4 inch 10 strand jumpers. The part number is WM10-04A-ND. These jumpers are a perfect replacement for the flex PC boards. The wires have the same spacing as the holes in the board and the 4Ē length is a perfect fit.

I made the mistake of installing the ribbon cable into the Dolby switch first. It is better to install it into the push switch first. That way you donít have to juggle the whole Dolby board when soldering to the push switch board.

LBPete
03-09-2007, 02:57 AM
OK everything back in place. Time to check it out. The good news was nothing smoked when I turned it on. The bad news was now I had major distortion on the left channel in the test tone and in Dolby FM. The meter on that side wasnít working either. After all this work, I had made it worse than it was. Shit.

Well I screwed around with it on and off for a few days and didnít get anywhere. Trying to trace the circuit in the manual and transfer that to the actual board is an exercise in futility. So I went to plan B. I invited CDFixer over for lunch.

I knew his week spot. All I had to do was flip on the scope and he just jumped right in. I donít think there is anyone on the planet that knows the Dolby board better then Jim. He is able to trace the circuit through the Dolby switch and in short order he found the first problem. Despite meticulous care in soldering the pass through, I had created this solder bridge that had shorted one the leads to the Dolby chip.

With the solder cleaned up, the Dolby FM and test tone were working normally but the meter still wasnít functioning. Jim dove back in and traced it to one of the back up jumpers I had installed on the push switch board. I must have been cross-eyed when I put it in because I connected it to the wrong point. Two problems down.

To me it was working and sounding good but Jim spotted a little surge in the meter when the tone switch was pushed. A little work with a volt meter and the schematic and he discovered a cap installed backwards. Hmmm, wonder who did that?

Well its working great now and I got to watch a master work his craft. It was a humbling experience. The man knows his stuff.

I hope this overview is helpful.

- Pete

alexkerhead
03-09-2007, 03:08 AM
Thanks for the guide Pete!

I might give that a go on my 8080DB sometime, and if I succeed, I might try it on my newly acquired 9090DB. :)

I didn't even know about the joints on the other side.

EchoWars
03-09-2007, 03:18 AM
Now the new ribbon cable can be installed. It is available from Digikey. Get the 4 inch 10 strand jumpers. The part number is WM10-04A-ND. These jumpers are a perfect replacement for the flex PC boards. The wires have the same spacing as the holes in the board and the 4Ē length is a perfect fit.They come with the ends dressed for soldering like that?

Anyway, I'd rather battle a pack of wild raccoons than tackle that project.:yes:

Bigears
03-09-2007, 08:43 AM
Wow!

gruntgravel
03-09-2007, 09:14 AM
Double WOW! That is impressive! I'm nervous about replacing a resistor to get the green light on.:tears: Any idea whats going on if you can only hear the Dolby test tone at >1/2 volume and the meters do not move? Is this an indication of a specific problem with the Dolby board?

Crazy
03-09-2007, 09:52 AM
:thmbsp:
Owning an 8080db that is my primary receiver for daily use..........this thread is of major interest and use to me!

We need far more of these type threads in this forum.:yes:

VERY WELL DONE!

Thank you for sharing your knowledge and putting out the effort involved in making this thread happen! :D

LBPete
03-09-2007, 10:48 AM
They come with the ends dressed for soldering like that?:Yes the jumper come with the ends dressed and tinned. Just plug them in and solder. They cost about $1 each.

Anyway, I'd rather battle a pack of wild raccoons than tackle that project.:yes: It will be a long time before I try this again.

- Pete

jpdylon
03-09-2007, 10:49 AM
Excellent thread Pete. Well documented :yes:

I cringe looking at those pictures trying to disassemble everything. The QRx-9001 has something like 54 pass through joints, and those are bad enough to get at even after dismantling the entire front of the machine and taking the board out. I would not want to mess with a 8080 or 9090db, 64 pass throughs and the PITA procedure to get to them?

You are a brave man.

LBPete
03-09-2007, 10:49 AM
Double WOW! That is impressive! I'm nervous about replacing a resistor to get the green light on.:tears: Any idea whats going on if you can only hear the Dolby test tone at >1/2 volume and the meters do not move? Is this an indication of a specific problem with the Dolby board?Just one of many symptoms of a Dolby board problem. Start by cleaning the switches.

- Pete

wsjoe
03-09-2007, 01:12 PM
LB/CD,

Great job in making all these procedure handy for all of us. This has to me the biggest problem of all Sansui models with DB. I have 4 8080DB's and 9090DB's that will need an overhaul like you did and will probably make alot more mistakes than you did, but then, CDfixer is two miles away from me.

wsjoe

englissa
03-09-2007, 02:45 PM
Pete I'm also in the process of recapping a couple 9090db's, I took a close look with a glass at the doby board and didn't see anything so i'm gonna give it a try without repinning it , you went through great pains doing what you did , nice job and great info englissa

CDFixer
03-10-2007, 11:14 AM
If you have a scope or a high impedance headphones you can test the Dolby inputs and outputs by scoping these points on the board.

Insert a tone into the AUX inputs of the receiver. If you have the same on the inputs and outputs in each of the Dolby Switch positions then the problem is not the Dolby board. Note: The Dolby FM position requires the function switch to be in the FM position and the inputs are about midpoint in the audio stream. If the Aux input works then the Dolby FM will probably work also.

Morden2004
03-10-2007, 12:36 PM
I have the ribbon cables back in and a quick test of the Dolby board shows I still have a missing channel. Back to bench checking -- but later as I had a system meltdown Thursday PM and I'm still trying to reload the system.

I had a SCSI controller failure and since my system drive is on 1 of the 2 SCSI's ... well, you get the picture :thumbsdn: It takes me about 10 hours to reload this system and I don't enjoy that call to Microsoft (India) to get the installation codes.

The SCSI's are now part of my junk box :scratch2: as I can't be bothered fixing them. They were only 36GB SCSI's anyway. I'm going to add a 500GB SATA.

Paul

LBPete
03-10-2007, 03:59 PM
Is the channel missing in the off position of the Dolby switch? Have you been able to tell if your Dolby board has the rivited pass throughs?

- Pete

Morden2004
03-11-2007, 06:22 AM
Is the channel missing in the off position of the Dolby switch? Have you been able to tell if your Dolby board has the rivited pass throughs?

- Pete

Yes, the channel is missing at the OFF position. I sucked the solder out of 1 pass-thru and as far as I can tell (it's my first Dolby board, so I don't have much history to fall back on) it is a rivet. I meter tested a dozen or so using my DMM with the circuit tracing on and they seem well but ... ???

I will pull the board out far enough for me to get a scope probe into it and start tracing signals. Perhaps I can isolate a section. :dunno:

Paul

CDFixer
03-11-2007, 09:03 AM
Yes, the channel is missing at the OFF position. I sucked the solder out of 1 pass-thru and as far as I can tell (it's my first Dolby board, so I don't have much history to fall back on) it is a rivet. I meter tested a dozen or so using my DMM with the circuit tracing on and they seem well but ... ???

I will pull the board out far enough for me to get a scope probe into it and start tracing signals. Perhaps I can isolate a section. :dunno:

Paul

Paul, here is my secrets to Dolby troubleshooting pages. Page one is the switch physical layout. Page 2 is the switch board layout, so you can trace from the Dolby board to the switch board and back. Page three is the signal flow with the switch in the off position.

PM me if you have questions about use of the document.

Morden2004
03-11-2007, 09:17 AM
Paul, here is my secrets to Dolby troubleshooting pages. Page one is the switch physical layout. Page 2 is the switch board layout, so you can trace from the Dolby board to the switch board and back. Page three is the signal flow with the switch in the off position.

PM me if you have questions about use of the document.

Unbelievable! Is this a great site or what? :thmbsp:

Thanks, Jim. There is absolutely no doubt that your document will save me hours of messing about on that ugly board. Tomorrow (if I can avoid actual paying work :sigh: ) I will start to trace. Are we betting that it's either a failed connection in the switch or a feed-thru? :yes:

It's raining here and temp about 7C (49'ish for you F-types). The snow is melting and our local fisherman is hauling new poles for the wier. I will need to make myself available when he's re-building this wier because it's one of the very last and it's always a reason for the villagers to gather and help.

Heck, if tomorrow is nice, I may have to skip work, Sansui repairs and happy hour! Damn. :drool:

Paul

CDFixer
03-11-2007, 10:38 AM
Are we betting that it's either a failed connection in the switch or a feed-thru? :yes:


Paul


Much better that it is a feed thru. There are two pots on the Dolby board that can also cause problems.

As a side note: When I am troubleshooting, I connect up to the AUX input a test tone and only to the channel that is not working. That way I don't lose focus.
Now about that happy hour-------:beerchug: :beer:

LBPete
03-11-2007, 11:32 AM
Paul, you are in the hands of the master but I would like to add a simple caution. Be sure to check the more mundane parts of the signal path like the tone control board and the function selector switch before jumping into the Dolby board. The tone defeat switches can cause channel drop too. The blue and gray wires carry the signal from board to board.

- Pete

CDFixer
03-11-2007, 01:45 PM
Paul, you are in the hands of the master but I would like to add a simple caution. Be sure to check the more mundane parts of the signal path like the tone control board and the function selector switch before jumping into the Dolby board. The tone defeat switches can cause channel drop too. The blue and gray wires carry the signal from board to board.

- Pete

Yes, the first test I do on the Dolby board is make sure the Dolby board is causing the problem by checking for the signal at the output of the Dolby board. See earlier post for a picture of the input and output points.

Signal flow through the receiver is

Input board and selector switch
Dolby board and switch and tape monitor switch board
Loudness and -20DB mute switches
Volume and Balance controls
Tone control and filter switches
Back to the input board, and preout to main jumpers
Driver board and outputs
Protection board and relay
Speaker selection switch
Speaker terminals.

LBPete
03-12-2007, 10:53 AM
To update a question that came up in another thread, the 9090DB and 8080DB use the same Dolby board. They are interchangeable.

- Pete

truenorth
03-13-2007, 12:33 AM
Pete/Jim,

Thank you guys for taking the time to document this troublesome DB board...
I spent this past weekend trying to fix my DB board sympton (distorted left channel...) by first cleaning all the controls with DeOxit. In the end I still wasn't able to fix the problem entirely. I must have partially removed the DB board a half dozen times in the process and to date I can now induce the problem by either pushing or slightly bending the DB and I can get either channels to distort.

It looks like my next step is to get in and remove the DB board entirely and do the time consuming resoldering job. I am saying resolding because I believe my issue is more related to something mechanical (ie poor connectivity) or at least this is what I am hoping for. One thing that really suprised me with my unit was the excellent condition it is in. I must have one of the last units made because all the components: caps, resistors looked "brand new", even the insulating sleeves are clean not discolored... My two power caps was about twice the size compared to yours in the picture and there was no dust whatsoever inside the unit.

For this reason, I must be really careful in removing the parts I am about to do. I hope that I don't have too many questions for Jim going forward. I will report back if I am successful or not. Wish me luck.

Cheers,

TrueNorth
(Norm)

LBPete
03-13-2007, 01:29 AM
If the symptoms change when you flex the Dolby board, you have pass through problems. Before taking it apart, see if you can isolate the part of the board that reacts to pressure and concentrate on the pass throughs in that area. You really want to avoid tearing the whole thing apart like I did. The opportunity for error is enormous.

If it has the riveted pass throughs, you should be able to reflow the solder. If it doesn't have the riveted pass throughs, then think about pining the pass throughs.

If you have a 9090DB, it will have larger filter caps than the 8080DB in the picture. The way to tell the production is by the serial number. It has a date code built in.

- Pete

CDFixer
03-13-2007, 01:01 PM
DITTO to LBPete.

I routinely just reflow the solder joints during troubleshooting. If you don't have a scope then take a careful look at all the feed thrus on the board. Look for any that look dull, have dimples or look like the edges are cracked.

If you are working without test equipment. reflow one joint the test and see if there is a change for better or worse. You don't want to get to where you have reflowed several joints then test and the problem is worst you then don't know which joint caused the new problem.

Morden2004
03-13-2007, 04:14 PM
DITTO to LBPete.

I routinely just reflow the solder joints during troubleshooting. If you don't have a scope then take a careful look at all the feed thrus on the board. Look for any that look dull, have dimples or look like the edges are cracked.

If you are working without test equipment. reflow one joint the test and see if there is a change for better or worse. You don't want to get to where you have reflowed several joints then test and the problem is worst you then don't know which joint caused the new problem.

Supplementary Q: Can you reflow the pass-thru's successfully from just one side? And if yes, what setting for the iron (30,40,50 watts)?

Paul

CDFixer
03-13-2007, 06:28 PM
Paul, I do this all the time, I use a butane powered soldering iron on the lowest setting. The iron should have enough wattage and be hot enough to quickly melt the solder, I think a 40 or 50 watt would work OK.

vanman
03-13-2007, 06:37 PM
how you test your work if the board is out of the unit?

steve

LBPete
03-13-2007, 10:59 PM
Supplementary Q: Can you reflow the pass-thru's successfully from just one side? And if yes, what setting for the iron (30,40,50 watts)?If your board has riveted pass throughs, the rivet will help conduct the heat to the other side. I think it's a little more iffy if it's not riveted. I'm not sure the copper pad on the opposite side will get hot enough to bond the solder.

You may be over thinking that fancy soldering iron looking for a specific watt setting. Like a good chef, you need to adjust the flame based on how the food is cooking.

- Pete

CDFixer
03-13-2007, 11:33 PM
how you test your work if the board is out of the unit?

steve


I don't work on the feed thrus with the board out of the unit. I have a scope and signal generator and I trace the signal thru the board and fix what needs to be fixed.

I work on the if it ain't broke don't fix it.

Morden2004
03-14-2007, 07:06 AM
I don't work on the feed thrus with the board out of the unit. I have a scope and signal generator and I trace the signal thru the board and fix what needs to be fixed.

I work on the if it ain't broke don't fix it.

That's my mantra too! :thmbsp:

Now, back to the board -- I'll be scope checking that board in place and if I suspect a pass-thru of failing I'll be attempting a repair with the board in place so that I can quickly check the results; Power off, solder re-flow, power on. :scratch2:

Of course, YMMV so this may not work.

Paul

silverHalo
03-17-2007, 01:27 AM
Besides the obvious names (Digikey, Mouser, Woodang) is there any favorite sites you guys have for acquiring parts?
I am most interested in hard to find transistors and other semiconductors.
Perhaps a thread on part suppliers? Kind of a mini-database for present and future members to reference? And perhaps rating the service and selection of companies we've previously ordered from? Any takers?

Nakdoc
03-17-2007, 04:57 AM
Electronica.com is good for silicon. They will go overseas for rare stuff.
BDent.com is good for research.

bookasan
03-17-2007, 12:23 PM
I use these two sites all day long at work since I get paid to find hard to find components.
These are distributor inventory search engines. You will need to register with EEM, but they don't ask for much and I have never received any spam from them.

EEM is a little better than Findchips since they only show suppliers with actual on hand inventory. I have found the inventory is dead nuts. If it shows 10 pieces and I call the distributor, they have 10 pieces.
Findchips shows distributors that carry the part whether they have stock or not, but it will show the on hand quantity.

I use both because not all suppliers are listed with both.

www.eem.com

www.findchips.com

bookasan
03-17-2007, 12:30 PM
Here are a few more catalog type places that carry many replacement parts as well

www.newark.com
www.alliedelec.com
www.mcm.com
www.partstore.com

Partstore.com is great for vintage electronics. You can type in the manufacturer then the model number and it will show you all parts for that model. That is where I found the replacement tweeters for my Yamaha NS1000's. I even found a replacemnt knob for my clothes dryer there.

silverHalo
03-17-2007, 12:51 PM
www.acme-sales.net - transistors (some hard to find) & semis, etc
www.ceitron.com - transistors (hard to find parts), semis, phono parts - fast service (about a week), original Sanken 2SA765's and Hitachi 2SC984's
www.partsexpress.com - various audio parts, speaker kits, etc
www.surplussales.com - crazy surplus parts
www.woodang.net - transistors (Genuine!) Sten from Sweden is great!
www.mcminone.com - Transistor & semis, etc
www.tritronicsinc.com - factory audio replacement parts
www.moyerelectronics.com - transistors, semis, etc
www.digikey.com - transistors, semis, just about everything else
www.mouser.com - on par with digikey

Always check out the minimum order fee for each company, usually around 25-30 bucks to avoid large handling fees!!

Morden2004
03-18-2007, 06:38 AM
I have made this thread a 'sticky thread' so that we can always access this terrific list of parts suppliers. Thanks to all who contributed to this list.

Paul

silverHalo
03-18-2007, 02:53 PM
www.audiolabga.com - transistors, semis, speakers, caps, tools
www.oaktreeent.com/Sansui_Stereo_Parts_Units.htm - Parted out Sansui's, lots of model specific items.... very expensive!
www.thetubestore.com - Vacuum Tubes & Orange Drop Capacitors
www.prelcoparts.com - Transistors, Resistors, Caps, Obsolete parts. Claim to have genuine Sanken transistors - unconfirmed.
www.allelectronics.com - Speaker Parts, cables, connectors, misc. parts and supplies

Morden2004
04-12-2007, 07:46 AM
FAQ 18: How do I clean the tuning capacitor? (reply by Dr*Audio)


It could be just that the tuning capacitor needs cleaned. In fact that is very likely. Here is how:
Cleaning a tuner

You need 3 things:
1. A non -residue contact cleaner, such as:
http://www.mcminone.com/search.asp?keyword=contact+cleaner&btnSubmit.x=12&btnSubmit.y=9
and
2. CAIG Cailube MCL, available also from MCM: {NOTE: may be discontinued
-- try http://www.mcminone.com/product.asp?product_id=20-885&catalog_name=MCMProducts instead}

3. Dustoff compressed air.
First, clean the inside of the tuner carefully with a vacuum cleaner. be careful not to bump any adjustments and stay away from the tuning capacitor.
Look at the tuning capacitor. You will see it has a bunch of fins on it like a radiator in a car. Turn the tuning knob so the fins move out of the chassis and are exposed. Clean the fins with the Dustoff, blowning them out thoroughly. use the plastic snorkel tube that comes with the Dustoff. Do not touch the fins with the tube!
The fins are located on a shaft. Where the shaft goes through the.chassis of the tuner there are copper or brass contacts that rub against the shaft and provide the connection from the shaft to ground. With the fins exposed, spray a small amount of the contact cleaner on the shaft where each contact touches it. Then rotate the tuning knob back and forth through it's complete tuning range 20 to 30 times.
Now allow it to dry. Then carefully squirt just a drop or 2 of the MCL on the shaft where the contacts touch it and then rotate the tuning knob a few times again to spread the preservative around.
When you are done, you may have to adjust the trim cap on the tuner for the local oscillator so that the stations come in at the correct place on the dial.
__________________
Warren

Morden2004
07-08-2007, 04:50 AM
FAQ #19: Access to speaker relay & meter lamps on 9090/9090DB


In the thread link below, Dr*Audio explains how to access the speaker relay, and tips on replacing the meter lamps with LED's.


http://www.audiokarma.org/forums/showthread.php?p=1238605&posted=1#post1238605

russ1965
07-20-2007, 08:40 AM
I Just got my last 9090db up and running after replacing the tunning capacitor. Checking it out everything seems OK except for the db circuit. The meters read Left .2, Right 3 (instead of 5) both in Rec 1 & Rec 2. Db FM seems to be slightly less power out on the left per power meter, than regular FM. I deoxit, db controls when I had it apart. There is still slight static db function switch. Once the receiver is run for 24 hours I going to take it apart again and use contact cleaner, as Pete suggested, deoxit again, and resolder any connections that look bad.

What would be a good starting point on checking the soldering connections.

Since I haven't done any major electronic repair since 1966-67, when every transistor had to really heat sheilded from the Weller 100/140 watt soldering gun. When you flow the solder, or just resolder a joint how do you heat shield the semiconductors. I can't get a needle nose pliers in the there. I do have adjustable soldering "station", I got for this project, what setting should I use around semiconductors. All this station has is 1 yellow 2 orange 2 red settings.

Thanks,

RJS

Morden2004
07-20-2007, 09:02 AM
I'll toss in my $0.02 worth of knowledge but I'd advise you to also wait for our (real) resident experts to chime in. :D

First, I use the lowest setting on my Weller station that will flow solder when working around SS devices. That's about 2 on my dial.

Next, I've had excellent success on those Dolby board pass-thru's and switch connections to the PCB by sucking all those connection points completely empty of solder. Then, I resoldered them with high quality solder. :thmbsp:

That is what I did to my project 990DB on it's 4th trip to the work bench after fixing it 3 times for intermittent and/or channel drop-outs. The first 3 trips I just reflowed existing solder and added some pins thru some of the pass-thrus. Then 1 or 2 weeks later, the left channel would drop out.

Using the above technique the last trip to the bench, that 990DB has been singning for more than 4 weeks this time. Not conclusive, but surely a good sign. :yes:


Paul

LBPete
07-20-2007, 10:37 AM
RJ, be real careful about opening a can of worms here. From your discription the problem may not be serious enough to risk making it worse by fooling with the dolby board.

The meters being off may be an adjustment. There is a procedure in the service manual to center them. If you are not using your 9090DB to add Dolby noise reduction to a tape recordings, the meter function is not critical. There are no Dolby FM broadcasts so that position of the switch is pretty much useless.

If you have normal, consistant stereo operation, and you don't use the Dolby function for recording tape, I wouldn't mess with the dolby board.

- Pete

russ1965
07-20-2007, 12:22 PM
Pete, I hear what your saying. I have made the db adjustment on my other unit. It was only off a little, and both meters were reading the same. Since this unit the meters aren't reading the same, .2 vs 3, i thought the meter adjustment was not in order. I have rarely used the db function for recording, since I still haven't transfered all my reel to reel tapes to cassette. Now none of cars have cassette.

The only time I would be using the db function is to bring up quality of recorded tape, while rerecording it, since the some of the tapes are begining develop problems, especially the Sony, out of 24, 7 are going bad, 7 I haven't played yet. Maxell out 51 I have only 1 bad one, (it was back coated), Scotch 1 bad. I think I have 50 more tapes to go through before I start recording, the bad ones, going through an equalizer and using db. It might be a project that will never get done, like the cassette.

Bob

LBPete
07-20-2007, 01:41 PM
If your tape decks have onboard dolby, there is no need to use the 9090DB's dolby function.

- Pete

russ1965
07-22-2007, 05:30 AM
Only the cassettes have db, the reel to reels don't. The problem tapes are all r to r, Sony tape's are PR-150, normal bias. How serious is the problem in the db circuit, with .2 L, 3 R. Does it require a complete rebuild, some part replacements, or just an adjustment as suggested earlier.

Thanks,
Bob

LBPete
07-22-2007, 10:46 AM
Start with adjustment.

- Pete

CDFixer
07-22-2007, 01:29 PM
As Pete states there is a complete adjustment of the Dolby system in the service manual. According to the user manual here is how the Dolby circuit is to be used.
(We are assuming the unit is calibrated)


Select record 1 or 2, and press the tone push button.

At the recorded set the record level to 0DB

Record a short period of the tone generated (about 30 seconds).

Press the tone push button and record the source.


When playing back, set the output listening to the tone at the beginning of the tape, to 0DB.

At the receiver set the Dolby control to play, and set the level to the center of the Dolby meters.

The system is now set to properly decode the Dolby encoded tapes.

These instructions are paraphrased, I will scan and post the instructions that are in the manual in another post.

russ1965
07-23-2007, 09:12 AM
As Pete states there is a complete adjustment of the Dolby system in the service manual. According to the user manual here is how the Dolby circuit is to be used.
(We are assuming the unit is calibrated)


Select record 1 or 2, and press the tone push button.

At the recorded set the record level to 0DB

Record a short period of the tone generated (about 30 seconds).

Press the tone push button and record the source.


When playing back, set the output listening to the tone at the beginning of the tape, to 0DB.

At the receiver set the Dolby control to play, and set the level to the center of the Dolby meters.

The system is now set to properly decode the Dolby encoded tapes.

These instructions are paraphrased, I will scan and post the instructions that are in the manual in another post.


Jim,

Thanks, I have the Operators manual and service manual, so no need to scan them. I have a question on the adjustment procedure. I will post that later since I am away from the service manual at the moment.

Thanks,
Bob

russ1965
07-23-2007, 10:38 AM
The Service Manual I have is D60720M. Referring to page 7 Section 4-1-2 Calibration Tone Volume & Dobly Meter Volume Adjustment.

1. Speaker Selection A
2. Master Volume Minimum
3. Balance Volume Center
4. Accessory Switch Off
a) Question What is the Accessory Switch, I am assuming that the Function Switch is not set to Aux Input, but is it set to, I think FM Auto.
5. Dolby Selector Switch REC 1

russ1965
07-23-2007, 10:42 AM
Step
1. Turn on the Dolby REC CAL TONE Switch.

2. Connect VTVM to the front Tape 1 REC terminal.
a. Question There is no Front Tape 1 REC on the outside of the receiver, I am assuming it is on the Dolby board, and the diagram that I have is not a clear copy where the terminal is on the board.

3. Adjust VR601 on the circuit board F-2655 to obtain 270mV on the indication of the VTVM.
4. Adjust both VR03 (L-CH) and VR04 (R-CH) on the circuit board, so that indicator of the power meter will be center of the Dolby mark.


Thanks
Bob

LBPete
07-23-2007, 11:31 AM
Use the Tape 1 jacks on the back of the receiver.

- Pete

Arkay
07-23-2007, 12:05 PM
This thread has been a fascinating read, and a good example of what makes this board such a special place.

It also makes me more grateful than ever before, that my 9090 does NOT have the "DB" letters tacked on the end! :D Nothing in a regular 9090 is nearly as challenging as that Dolby stuff looks! :no:

russ1965
07-27-2007, 10:22 AM
Use the Tape 1 jacks on the back of the receiver.

- Pete

Pete,

Set VTMV to AC on Left got 266mv, Right got 299mv Dolby Meters Left .2 Right 3. Did not adjust VR601, since the voltage was in the middle of the 270mv setting required. Is there any max not to exceed. Which to you adjust too, Left or Right?,

Checked two other 9090db's got: A) Left 290mv, Right 288mv, Dolby Meters centered at 5. B) Left 188mv, Right 186mv, Dolby Meters at 4 . Refering to my friend's units, does the variance between the Left & Right 33mv on my unit cause the problem of difference .2db left, 3db Right on the Dolby Meters?

Bob

pioneernut
07-27-2007, 02:02 PM
Would it be to much trouble to get a scan of the manual regarding the section on Calibrating the Dolby level from anyone who has it. I've got a stand alone Advent Dolby encoder/decoder, and I want to fix it up, but I have no information on how use these outboard decoders. This would probably help as I can't find sqwat about mine.
Thanks Mike

Morden2004
07-27-2007, 04:53 PM
Here ya go:

http://www.clarkeworks.com/images/9090db_Dolby{1}.jpg
http://www.clarkeworks.com/images/9090db_Dolby{2}.jpg

Paul

LBPete
07-27-2007, 05:18 PM
Pete,

Set VTMV to AC on Left got 266mv, Right got 299mv Dolby Meters Left .2 Right 3. Did not adjust VR601, since the voltage was in the middle of the 270mv setting required. Is there any max not to exceed. Which to you adjust too, Left or Right?, To get them both the same, you need to do the input level adjustment first. These values are not super critical. Just get them close.

Checked two other 9090db's got: A) Left 290mv, Right 288mv, Dolby Meters centered at 5. B) Left 188mv, Right 186mv, Dolby Meters at 4 . Refering to my friend's units, does the variance between the Left & Right 33mv on my unit cause the problem of difference .2db left, 3db Right on the Dolby Meters? Did you adjust the meter centers with VR03 and 04? If not, give it a try. There are holes in the dolby board to access the back side of these trimmer pots. They are covered with a little piece of cloth so you have to kind of deflower them before making the adjustment.

- Pete

LBPete
07-27-2007, 05:24 PM
Another thing to check is the output of the tuner power supply. It powers the dolby board and meter functions. The output of the power supply is often high which can make the meters read high. The output should be 12.5v and there is a trimmer on the PS board to adjust it. Measure the output on the red lead at Pin 01. It's the one that the big cap connects to. There is no mention of this adjustment in the service manual.

- Pete

pioneernut
07-28-2007, 12:15 PM
Thanks Paul,,, appreciate it alot
- Mike

CDFixer
07-28-2007, 03:33 PM
You must adjust the tuner power supply first! Then do the adjustment for the input level (VR01 and VR02), Requires a signal generator with an 80mv output. Then adjust VR601 to adjust the output level, then adjust VR3 and VR4 to center the meters. That should calibrate the Dolby system.

russ1965
07-29-2007, 07:37 AM
Thanks Pete & Jim,

Did haven't have a signal generator. I used my cassette deck that generates a 400 htz for dolby and adjusted output to 80mv. Fed to aux input, and did the input adjustment. All VR on the dolby board had the clothe coverings. Both channels were off 520mv 600mv. I then activated the dobly on the 9090db, the dolby meters then read left 17db, right 5db. vs -2db left and 3db right.
This is were I probably went wrong. The manual says to adjust VR 601 at Tape 1 REC terminal to 270mv. What Jim just said is that it adjusts the Output. I had VTVM measuring the REC Left 339vm, adjusted to 270mv, Rec Right read 341mv adjused to 270mv. Read Left it then read 341mv. Went back and forth until both the Left and Right read aprox the same, which was 291mv 310mv. I then adjusted the VR03 and VR04, to center. That was yesterday afternoon.
This morning I read Jim's post and remeasured everything. Everything was the same except VR601 adjustment the Left Reads 340mv, and the Right reads 404mv. The Left Dolby Meter is hair line below 5db. When adjusting VR601 what channel left or right is adjusted too, and the is VTMV is attached to the Tape 1 REC or to Tape 1 Playback.

Thanks,

Bob

CDFixer
07-29-2007, 12:54 PM
The output level is measured at the REC terminals. The input level controls VR01 and VR02 need to be adjusted first they will affect the VR601 adjustment. When adjusting VR01 and VR02 you need to make sure the input to each channel is the same. If the input adjustments are not the same then the adjustment for VR601 will not be the same as that signal flows through the VR01 and VR02 adjustments controls. VR03 and VR04 are adjusted last and are only for the calibration of the meters. These adjustments will not adjust the output but the others will affect the meter calibration.

russ1965
08-08-2007, 07:07 PM
Jim & Pete,

Redid everything and everything smooth. Thanks for your help

Bob

LBPete
08-09-2007, 01:19 AM
Good to hear that you got it all sorted out.

- Pete

archie2
08-14-2007, 11:57 PM
Pete, what happens if there is no Dolby test tone? I did your calibration test on my 8080DB and heard no tone and the right power meter only, moved with the power output. Yet everything works as it should and it's a very nice sounding receiver in all aspects.

LBPete
08-15-2007, 01:37 AM
If you don't get a Dolby test tone on both channels, there is a fault on the Dolby board. If you don't use the dolby function, and it plays on both channels when the Dolby switch is in the off position, don't worry about it.

- Pete

archie2
08-15-2007, 08:07 AM
If you don't get a Dolby test tone on both channels, there is a fault on the Dolby board. If you don't use the dolby function, and it plays on both channels when the Dolby switch is in the off position, don't worry about it.

- Pete

Thanks Pete, I tried the test tone again this time with the volume turned to 1:00 and I heard it right channel only. But I never use Dolby so thanks for the assurance, I won't worry about it.

LBPete
08-15-2007, 11:30 AM
It won't hurt anything for your own use but if you plan to sell the unit, you should disclose the fault. A potential buyer should know what he's getting.

For that matter, anyone looking to by a 9090DB or 8080DB, should ask if the test tone and meters work on both channels.

- Pete

CDFixer
08-26-2007, 09:53 PM
Well I have broken the myth of the Sansui "Dynamic Oval Capacitors" I have been recapping my G-9000 and wanted to preserve the look so I took one of the OVALS apart and this is what I found.

Two round capacitors inside the oval can.

See pics below.

Bigears
08-26-2007, 09:59 PM
Great info Jim. Now if you can find two similar size modern caps, you can use hot melt or wax and stuff it all back into the oval cans for that OEM look!

ManyMoonsAudio
08-26-2007, 10:04 PM
Files arent working jim

luvvinvinyl
08-26-2007, 10:08 PM
They worked for me, just fine. Firewall issue, perhaps?

CDFixer
08-26-2007, 10:09 PM
I have already done that. See the photos below

CDFixer
08-26-2007, 10:10 PM
Files arent working jim

You will need Adobe reader 5.0 or higher to see the files.

Duffinator
08-26-2007, 10:14 PM
Good work Jim! So the outside cover can be salvaged? What caps are you using for replacements and are these the same oned in an AU-919?

CDFixer
08-26-2007, 10:19 PM
Here are the files as JPGs

CDFixer
08-26-2007, 10:26 PM
They are not the same the ones in the 919 are 63V where the ones in the G-9000 are 80V. I don't know if the Physical size is the same or not.

The caps I used are 15000 UF 80V I put them in parallel for a total of 30000UF. I am going to test to see how that works. I may have to get some 10K or 12K if that proves to be too much.

DENNYDOG
08-26-2007, 10:30 PM
I wonder why Sansui did this? Maybe to make everyone think the oval capacitors were better because they "looked" new and different and maybe better than anything else?

CDFixer
08-26-2007, 10:32 PM
They actually came apart pretty easily. I clipped the shrink on the cap so that the entire bottom was exposed and them drilled several holes in the plastic bottom, I then cut the plastic and removed it. The Capacitor portions pulled out really easy as did the wax that was surrounding the caps. I then had a empty shell and found that that fit perfectly over the caps that I had mounted in the unit.

QuadBob
08-26-2007, 10:35 PM
They are not the same the ones in the 919 are 63V where the ones in the G-9000 are 80V. I don't know if the Physical size is the same or not.

The caps I used are 15000 UF 80V I put them in parallel for a total of 30000UF. I am going to test to see how that works. I may have to get some 10K or 12K if that proves to be too much.

Excellent post Jim!!

I've got my own G-9000db, G-9000 and AU-919 that I was going to eventually explore this issue.

Question........was it difficult to "gut" the oval caps? How did you remove the originals?

On the increased capacitance........The G-9000 should be fine with it's soft start circuit!

Congrats!

QB

CDFixer
08-26-2007, 10:48 PM
QB, I am going to do two more and will post some pictures of the process as I go along. It is a lot!!!!!!! easier than I thought it would be, based on my experience with other caps.

nosirrah
08-26-2007, 10:55 PM
QB, I am going to do two more and will post some pictures of the process as I go along. It is a lot!!!!!!! easier than I thought it would be, based on my experience with other caps.

And this my friends, from the same man who brought you Frankensui !!!!!
I gotta send you some AU 7500's, it's way too obvious you have far too much free time on your hands.
But a real fine fix to make that G look bone stock, probably go to some other tech in a few years and have that guy scratching his head...:scratch2:
Casey

targeteye
08-26-2007, 10:58 PM
Wound in opposite directions to cancel out inductance?

CDFixer
08-26-2007, 11:07 PM
Nope, both wound in the same direction.

Wound in opposite directions to cancel out inductance?

CDFixer
08-26-2007, 11:10 PM
That's the way it is when you are retired. Way too much time on my hands. I just have to sneak past the "honey do's" in the morning.

And this my friends, from the same man who brought you Frankensui !!!!!
I gotta send you some AU 7500's, it's way too obvious you have far too much free time on your hands.
But a real fine fix to make that G look bone stock, probably go to some other tech in a few years and have that guy scratching his head...:scratch2:
Casey

LBPete
08-26-2007, 11:55 PM
Very nice Jim. Thanks for the pics.

- Pete

Morden2004
08-27-2007, 05:57 AM
Well I have broken the myth of the Sansui "Dynamic Oval Capacitors" I have been recapping my G-9000 and wanted to preserve the look so I took one of the OVALS apart and this is what I found.

Two round capacitors inside the oval can.

See pics below.

Excellent news reporting, Jim. :thmbsp: This will certainly make restoration of these oval caps possible.

Paul

EchoWars
08-27-2007, 06:05 AM
Let's see a pic of the wiring side. Gonna be a bit trickier.

noveltone
08-27-2007, 06:17 AM
very interesting surgery! Thanks! :lurk:

Hyperion
08-27-2007, 11:20 AM
Arising from CDFixer's excellent work - the "unobtainium" oval psu caps used in the AU-919 are now technically back on the "obtanium" list !

This is was one big obstacle for me to try and obtain an AU-919 - I reckoned (with the help available here :yes: :banana: ) that I could just about deal with the semiconductor availability issues for this model - if I ran into problems. However with the main caps being "special" this was the "last straw" and thus ruled the model out for me.... up until now...

John

CDFixer
08-27-2007, 12:23 PM
You are right Echo, I did one set and was not really happy with the results. I am going to do the other side a little differently and I think it will be a better solution. I will post pictures when I am happy with the results.

Let's see a pic of the wiring side. Gonna be a bit trickier.

CDFixer
08-27-2007, 04:42 PM
Here are some pictures of the disassembly that I finally came up with that will work to make perfect replicas of the caps. A big plus it will not require any rewiring when done. I don't have the caps that I need to do that project but will have them later this week. The caps I have are too tall to totally fit inside the old can so I am ordering some new ones that are shorter. I will post those pictures later.


The first ones I did I destroyed the bottom piece, but after looking at the way they were assembled figured I could remove the bottom piece intact.

Here is that process
I start with the cap lightly clamped in a vise. (picture 1)

First cut the shrink from around the bottom of the capacitor. ( picture 2)

Then I remove lift the edge of the metal case and remove the rubber seal (picture 3)

CDFixer
08-27-2007, 04:49 PM
Continued disassembly

I then cut the metal edge flush with the bottom piece (picture 4)

Remove the bottom piece intact (Picture 5)

Cut the connections to the internals and remove the bottom piece (picture 6)

Remove the internals Move them back and forth a little and they will pull right out. (Picture 7)

Then remove the wax, It is pretty soft, usually comes out in a couple of pieces. (Picture 8)

CDFixer
08-27-2007, 04:52 PM
To finish off I clean up the edge of the case and add a small strip to prevent getting cut on any sharp edges that may exist.

As I said before the caps I have are too big to fit in the can and allow the cover to be put back on, I am ordering some and will show those results later this week.

Here is a picture of the wiring that I did on this unit I am working on now. I used the metal ground bracket so I did not have to re-solder the ground connections. I cut the connectors off the power wires and soldered them to the appropriate connectors on the new caps.

tabberski
08-28-2007, 09:58 PM
Is there anyone out there who would like to take on a similar job.. 9090DB Very little sound out of one side. Dolby rod is moving.. I live in St. Paul, Minnesota.

DENNYDOG
08-29-2007, 07:28 PM
I would think as thin as the case is, you could probably use a plier and pry the bottom lip back to get the old caps out. Then bend the lip back over after the new caps are installed in the case.

Don't you think this would work instead of cutting the bottom of the case off?

CDFixer
08-29-2007, 10:06 PM
I thought about that, this is still a work in progress. I have some new caps coming and will dismantle some more next week. I will post pictures.

CDFixer
09-01-2007, 12:04 PM
I have completed the oval capacitor restoration. My final solution keeps the caps completely like they were physically. The capacitance is increased to 24000 (up form 15000). They will mount exactly like the originals and when mounted you should not be able to tell that they are not original.


Here are some pictures. I used Panasonic 12000UF 80Volt caps, I used the 40X50MM size as these fit inside the original case.

I used hot melt glue to keep the caps in place

CDFixer
09-01-2007, 12:06 PM
The last four pictures.

I masked and painted the bottom so that it looks a little better but will never be seen.

Morden2004
09-01-2007, 12:19 PM
That looks super! I think you need to go into production :yes:

:lmao:


Paul

bucolicbuffalo
09-01-2007, 02:27 PM
You will need Adobe reader 5.0 or higher to see the files.


kpdf and SimplyMEPIS Linux opened them just fine. Great picture sequence.

PC Bob
09-01-2007, 08:46 PM
kpdf and SimplyMEPIS Linux opened them just fine. Great picture sequence.

I use DownThemAll (Free) and it loaded them just fine, too.

nosirrah
09-02-2007, 02:41 AM
Nice work Jim, and solved a long standing issue too...early candidate for DIY post of the year anyone?
Casey:banana:

LBPete
09-02-2007, 11:21 AM
Very nice Jim. The look of those oval caps are one of the things that makes the G-9000 what it it. You also find them in the AU-919 and maybe some of the other big Sansui amps of the era.

- Pete

ManyMoonsAudio
09-02-2007, 11:47 AM
Looks good Jim!

CDFixer
09-02-2007, 09:47 PM
Thanks, to all for the complements.

tarior
09-04-2007, 12:08 AM
Well I have broken the myth of the Sansui "Dynamic Oval Capacitors" I have been recapping my G-9000 and wanted to preserve the look so I took one of the OVALS apart and this is what I found.

Two round capacitors inside the oval can.

See pics below.

I just KNEW it would be something like that !!!

Great post btw, I know it will save me some R&D in the near future.

noveltone
09-04-2007, 07:46 AM
great work!

Njord Noatun
11-03-2007, 10:48 AM
The aluminum of the faceplate is polished with a metal polish like Semichrome polish.

Is this (http://buyitnow64.stores.yahoo.net/sipo.html) the product you are using to clean up alu face plates, Pete?

I have been using clearcoat safe automobile finish waxes with a minimum of abrasion such as Carnauba for my face plates - have you found the Simichrome to be more effective?

That 'Sui looks great, BTW :thmbsp: !

LBPete
11-03-2007, 10:56 AM
That's the product. Some autoparts stores and motorcycle shops carry it. One tube lasts forever. Semichrome is a very fine abrasive polish. So it's more of a cleaner to remove oxidation. Apply the wax after cleaning with the semichrome to give a protective coating.

I haven't tried waxing faceplates. They often have a "brushed" aluminum finish that has a lot of texture. The texture may trap wax and not look so good.

- Pete

Njord Noatun
11-03-2007, 01:42 PM
I haven't tried waxing faceplates. They often have a "brushed" aluminum finish that has a lot of texture. The texture may trap wax and not look so good.

Your objections against wax do make a lot of sense, Pete: In fact, I have one or two receivers - my 2285B springs to mind - with really textured face plates, and I have noticed that a few weeks after having cleaned and waxed the aluminum, it starts to look somewhat dingy again. I will re-clean it and see if it does the same without the wax.

Having said that, oxidation happens because the bare metal is exposed to the elements (the air at my house is not only humid, it is also extremely salty to the extent that you can literally smell the salt), and it would be nice to provide some kind of surface protection to prevent, or at least slow, re-oxidation.

If not wax, what do you guys thinking of wiping down the face plate with something like WD-40, in order to somewhat seal it from the elements?

Best,

spaceman
11-03-2007, 03:01 PM
I'm glad you brought this thread back up, Njord Noatun, & thanx for starting it LBPete. On my QRX-5500A, the acrylic is mostly good, but has a few small scratches right where the dial pointer sits, when I'm tuned into my favorite station. Lucky for me, there's no writing on the acrylic itself, so I'll be able to polish up both sides, if necessary. :yes:

cali9dub
11-03-2007, 05:16 PM
or you could just sand it and then buff with Novus products...much quicker and easier.

Greyhawk17
11-03-2007, 06:16 PM
Howdy Pete,
Excellent post, very informative,...Next one you repolish, acquire a polishing
compound sold at jeweler's supply, called ZAM, you will find to be superior
to other compounds, and if a power buffer is used 1720 rpm, or less. I have
been an artist/goldsmith for 38 years, and use it frequently....I also use the
Simichrome polish, good stuff.....Cheers!

LBPete
11-03-2007, 07:37 PM
Your objections against wax do make a lot of sense, Pete: In fact, I have one or two receivers - my 2285B springs to mind - with really textured face plates, and I have noticed that a few weeks after having cleaned and waxed the aluminum, it starts to look somewhat dingy again. I will re-clean it and see if it does the same without the wax.

Having said that, oxidation happens because the bare metal is exposed to the elements (the air at my house is not only humid, it is also extremely salty to the extent that you can literally smell the salt), and it would be nice to provide some kind of surface protection to prevent, or at least slow, re-oxidation.

If not wax, what do you guys thinking of wiping down the face plate with something like WD-40, in order to somewhat seal it from the elements?

Best,Be careful with WD-40. It may react with the painted letting. It will also leave an oily film that is likely to hold dust. All the exposed aluminum you see on these receivers has been anodized. It is a process that leaves a very hard coating of aluminum oxide on the surface. This is a very effective coating. It will not oxidize in the same way that raw aluminum will. All bets are off with salt air though. It can pit with constant exposure. Looking at some of the information on Simichrome, it states that it leaves a protective coating. It may be all you need. If you can get an even coat of wax onto it, that may be better.

I've done several face plates since starting this thread and would like to clarify a couple of points. 320 and 400 grit sandpaper is very coarse for acrylic. Only use these grits if the scratches are very deep. Otherwise try 1200 first and see if it cleans up. If not, try 600 followed by 1200.

I'll look into the ZAM and Novis products if they will simplify the process.

- Pete

Greyhawk17
11-03-2007, 08:07 PM
Howdy,
There is a silicone sealer/wax used for metal bathroom fixtures that will
protect aluminum trim, but am blank on the product name, have used it
sucessfully some years ago,....I'd visit Ace hardware, or similar store and
shelf 'hunt'........Cheers!

russ1965
11-06-2007, 06:41 AM
Novis products have been recommend for soft acrylics, like convertable rear widows. What I have used on acrylic face plates is Plexus sold at marina canvas shops where I got. Made by BTI Chemcial of Oak Park Ca. They have a web site. It works great. No problems, put it on 3 years ago. It is also anti-static. I originally bought it for convertable rear window, not so great. I am going to buy Novis for convertable window, when I put away for the winter.

Pete, How do you get such clear pictures, no reflections, what settings to you use.

LBPete
11-06-2007, 10:57 AM
To get clear pictures with no reflection you have to play with the camera angle. If that doesn't work, then you have to identify the source of the reflection and black it out. I often use a tripod but don't remember this particular set up. It's an old thread.

- Pete

joekid
11-06-2007, 11:51 AM
I have been using Mirror Glaze cleaner and polish plus Micro-gloss liquid abrasive.for years on Aircraft windsreens , instrument panels ,turntable dust covers and anything else that looks like plastic
Joe:thmbsp:

mswer
11-09-2007, 01:40 PM
Great instructions Pete. Recently picked up a somewhat rough 9090 DB (that needs more than cosmetic work, incidentally, so Sui heads keep your eyes open for a post on that soon) and it will definitely be receiving this treatment - thanks!

Morden2004
01-10-2008, 10:19 AM
FAQ #20: Dolby Circuit Performance Check submitted by: LBPete



There has been a lot of discussions about the Achilles heal of the 9090DB/8080DB, the Dolby circuit. It can cause a variety of channel dropping problems and can be hard to fix. In other cases, you may loose some of the Dolby circuit functionality and not know it. Here’s a simple check to see if all the Dolby functions are working.

Keep in mind there are many causes for channel dropping. Before pointing fingers at the Dolby circuit, be sure that all the controls are clean. An often overlooked point are the tone control turnover/defeat switches on the 9090DB. If they are dirty, you can drop one or both channels.

So, assuming that you have clean all the controls and that you have good sound from both channels, lets check the Dolby functions. Before starting set the Play Cal and Rec Level pots to minimum, all the way counterclockwise. Tune in a radio station or play some recorded media through the Phono or Aux input. Set the volume to a comfortable level.

Turn the Dolby selector to Rec 1 and press the Meter Rec Cal Tone button. The music should be cut off and you should hear a 1,000 Hz tone equally from both channels.

http://www.audiokarma.org/forums/attachment.php?attachmentid=74027&stc=1&d=1199773188


The power meter needles should center in the Dolby Symbol.

http://www.audiokarma.org/forums/attachment.php?attachmentid=74028&stc=1&d=1199773188

If you don’t get a clean even test tone from both speakers, or if the meters go dead, you may have Dolby circuit issues. If you have a good test tone, and the meters respond but don’t center, your Dolby circuit is out of adjustment. The calibration procedure is outlined in the service manual. It requires feeding a 400 Hz test signal into the Tape input so you need a signal generator to do it properly.

Next, return the Meter Rec Cal Tone button to the meter position. Set the Dolby selector to the Rec 1 position and turn up the Rec Level knob.

http://www.audiokarma.org/forums/attachment.php?attachmentid=74029&stc=1&d=1199773188

The music output should increase as you turn up the Rec Level. The maximum volume is still controlled by the volume knob so the Rec Level control will only bring the volume up to wherever the volume control is set. You should have good clean sound from both channels.

Turn the Dolby knob to Rec 2 and repeat the process. You should have good clean sound from both channels.

Return the Rec Level to the minimum setting and turn the Dolby knob to the Play position. Then turn up the Play Cal knob.

http://www.audiokarma.org/forums/attachment.php?attachmentid=74030&stc=1&d=1199773188
It should raise the sound level the same way the Rec Level knob did. You should have good clean sound from both channels.

Turn the Dolby knob to the Dolby FM position. You should hear FM broadcast from both channels. (Be sure you are tuned on a strong station). The sound quality in this position should sound on the trebly side. Some people prefer this sound to the Play position. Again, you should have good clean sound from both channels.

http://www.audiokarma.org/forums/attachment.php?attachmentid=74031&stc=1&d=1199773188

If you have good clean, even sound from both channels in all these tests, your Dolby circuit is healthy. If the meters didn’t center, calibration is only necessary if you plan to use the Dolby function to encode and decode Dolby NR through the tape inputs.

If you have drop out in one or more of these tests, the Dolby system has issues. If you don’t use the Dolby function, and you have both channels working when the Dolby knob is in the Off position, there is no harm in running it that way.

- Pete

LBPete
01-19-2008, 08:40 PM
Here are a collection of Bias Current and DC Offset adjustment procedures collected from various threads. Thought it might be helpful to post them all together. As this thread has grown over time, many members have made contributions. Many of these links originate as posts in this thread. These posts often have additional information so be sure to scroll through to see what is available.

Many thanks to all the members that have contributed.

PLEASE NOTE: This tread is primarily an information reference. Most users do not read or follow this thread beyond the first reference page. If you need technical help, you will get a better response by starting a new thread in the main Sansui Forum.

- Pete

9090DB and 8080DB (http://www.audiokarma.org/forums/attachment.php?attachmentid=31248&d=1164073353)

9090 and 8080 (http://www.audiokarma.org/forums/attachment.php?attachmentid=75945&d=1201141945)

7070 (http://www.audiokarma.org/forums/attachment.php?attachmentid=31227&d=1164065620)

5050 and 6060 (http://www.audiokarma.org/forums/attachment.php?attachmentid=31502&d=1164263592)

881 (http://www.audiokarma.org/forums/attachment.php?attachmentid=76109&d=1201244489)

G-2000 and G-3000 (http://www.audiokarma.org/forums/attachment.php?attachmentid=24652&d=1156899498)

G-4700 (http://www.audiokarma.org/forums/attachment.php?attachmentid=87157&d=1208104319)

G-5000 (http://www.audiokarma.org/forums/attachment.php?attachmentid=87156&d=1208104319)

G-6000 and G-7000 (http://www.audiokarma.org/forums/attachment.php?attachmentid=50085&d=1180143229)

G-7500 (http://www.audiokarma.org/forums/attachment.php?attachmentid=144891&d=1238996300)

G-9000/8000 (http://www.audiokarma.org/forums/attachment.php?attachmentid=144884&d=1238995746) - G-9000/8000 #2 (http://www.audiokarma.org/forums/attachment.php?attachmentid=144885&d=1238995746)

G-9700/G-8700DB (http://www.audiokarma.org/forums/attachment.php?attachmentid=113708&d=1224439275) Also see discussion in posts 51-59 of this thread
G-9700-1 (http://www.audiokarma.org/forums/attachment.php?attachmentid=113709&d=1224439275)
G-9700-2 (http://www.audiokarma.org/forums/attachment.php?attachmentid=112024&d=1223445078)
G-8700DB-1 (http://www.audiokarma.org/forums/attachment.php?attachmentid=113710&d=1224439275)

2000A/X (http://www.audiokarma.org/forums/attachment.php?attachmentid=185820&d=1261507827)

4000 (http://www.audiokarma.org/forums/attachment.php?attachmentid=100637&d=1216836600) - 4000#2 (http://www.audiokarma.org/forums/attachment.php?attachmentid=100638&d=1216836600)

Eight (http://www.audiokarma.org/forums/attachment.php?attachmentid=75104&d=1200610181) - Eight#2 (http://www.audiokarma.org/forums/attachment.php?attachmentid=75103&d=1200610181) - Eight Adjustment Discussion-see post 25 (http://www.audiokarma.org/forums/showthread.php?t=405735&page=2)

Seven (http://www.audiokarma.org/forums/attachment.php?attachmentid=68820&d=1195525674)

QRX-7001 (http://www.audiokarma.org/forums/attachment.php?attachmentid=131386&d=1232866271)

QRX-7500 (http://www.audiokarma.org/forums/attachment.php?attachmentid=94538&d=1213076010) - QRX-7500#2 (http://www.audiokarma.org/forums/attachment.php?attachmentid=94539&d=1213076010)

QRX-9001/8001 (http://www.audiokarma.org/forums/attachment.php?attachmentid=304012&d=1318523539)

AU-222 (http://www.audiokarma.org/forums/attachment.php?attachmentid=182842&d=1259975706)

AU-20000 (http://www.audiokarma.org/forums/attachment.php?attachmentid=91137&d=1210793650)

AU-5500 (http://www.audiokarma.org/forums/attachment.php?attachmentid=294318&d=1313945395)

AU-919 #1 (http://www.audiokarma.org/forums/attachment.php?attachmentid=131372&d=1232855330) AU-919 #2 (http://audiokarma.org/forums/attachment.php?attachmentid=131373&d=1232855330)

AU-9500 (http://www.audiokarma.org/forums/attachment.php?attachmentid=177046&d=1257087027)

AU-9900A/1100A (http://www.audiokarma.org/forums/attachment.php?attachmentid=89876&d=1209852837)

AU-717/517 (http://www.audiokarma.org/forums/attachment.php?attachmentid=82207&d=1205129320)

AU-719 (http://www.audiokarma.org/forums/attachment.php?attachmentid=177416&d=1257229283)

AU D22/AU D33 (http://www.audiokarma.org/forums/attachment.php?attachmentid=165150&d=1250589291)

AU-X701/901 (http://www.audiokarma.org/forums/attachment.php?attachmentid=92399&d=1211714170)

BA-2000 (http://www.audiokarma.org/forums/attachment.php?attachmentid=216407&d=1277081185)

naderpe
01-20-2008, 05:24 AM
Thanks LBPete, I could use the one for the 6060.
Is that a typo error on the original Sansui manual for VRo4 and VRo3,...are there any more typo's in that manual that you know of? If it is a typo it explains my difficulty making that adjustment.
Peter

LBPete
01-20-2008, 11:40 AM
If I remember correctly, there are two board variations for the 6060. The service manual has the procedure for the earlier one. If you have the latter variation, the service manual may not be correct. It was discussed in other threads. Try doing a search.

Sansui doesn't always identify the trimmers correctly. So if you are not seeing change when you turn one, stop and check your meter and setup. On most of these units, a tiny bit of movement results in a big change on your meter.

If the setup is correct, try the other trimmer. This type of error is more likely to happen with units that have offset and bias trimmers. Judging by the 6060 diagram, it only has a bias adjustment so the only possible error is left or right channel and that should be fairly easy to identify.

- Pete

sjcruiser
01-21-2008, 02:33 PM
Right on time - I've just acquired an 8080DB and this will get me started on the learning curve :)

Thanks Pete!

Regards,
Frank.

Njord Noatun
01-21-2008, 02:56 PM
Here are a collection of Bias Current and DC Offset adjustment procedures colleced from various threads. Thanks for posting that, Pete.

Are these documents already in Morden's database? It would nice to have all AK Sansui material in one easily accessible location.

LBPete
01-21-2008, 06:11 PM
All these images reside on the AK server from other posts. I just collected them here for convenience.

- Pete

ccheath
01-21-2008, 06:18 PM
Darn. I was hoping 5000A. I keep finding 5000X Service Manual. Is 5000A and 5000X identical in circuit? I been skeptical of using that Service Manual.

johnny_fever
01-21-2008, 06:20 PM
Good Job Pete. This Info sure comes In handy. Thanks Rick

CDFixer
01-21-2008, 11:09 PM
Thought I would post my tool for adjusting the 8080/9090 and DB units bias, It is a blown fuse, wires and a couple of connectors that the meter probes will fit into.

Morden2004
01-22-2008, 06:02 AM
Thanks, Pete. I guess this qualifies as yet another great FAQ. :thmbsp:

As soon as I get a moment, I'll send this thread to the FAQ section.

Paul

LBPete
01-22-2008, 10:51 AM
Can it be left open to add more procedures?

- Pete

Vehto
01-22-2008, 09:56 PM
Thanks for the info and tool very helpful. is the bias offset for 9090 same for 9090db ?

johnny_fever
01-22-2008, 10:08 PM
Hi CDFixer, I remember when you told me about your fuse tool. I will make one next time I adjust the 990/9090db. Later Rick

LBPete
01-23-2008, 01:07 AM
Thanks for the info and tool very helpful. is the bias offset for 9090 same for 9090db ?
No, the 9090 and 9090DB are different. Here's the procedure.

- Pete

sjcruiser
01-23-2008, 12:51 PM
No, the 9090 and 9090DB are different. Here's the procedure.

- Pete

Pete,

Didn't you mean to post the 8080/9090 page instead?

LBPete
01-23-2008, 08:32 PM
Sorry, I though I had already posted the 9090 procedure. It is the same basic procedure as the 9090DB but the values are different. The bias current for the 9090 (Model A) is set to 50 mA. The 8080 (Model B)is set to 30 mA.

- Pete

Morden2004
01-24-2008, 08:07 AM
Can it be left open to add more procedures?

- Pete

Certainly! As soon as you think we've covered the majority of units, I'll re-post in the FAQ's. I can still add more to it after -- so don't fret about it :D

Paul

Vehto
01-24-2008, 11:05 PM
Thanks for the bias offset info, off I go. I wonder what the bias offset values are for the 881 ? Where do you get the documentation is it part of the service manual ?

LBPete
01-25-2008, 01:01 AM
These procedures are from the service manuals. Here's the 881.

- Pete

Vehto
01-25-2008, 05:25 PM
very grateful Thank you Pete !!

CDFixer
01-26-2008, 11:47 PM
Sorry, I though I had already posted the 9090 procedure. It is the same basic procedure as the 9090DB but the values are different. The bias current for the 9090 (Model A) is set to 50 mA. The 8080 (Model B)is set to 30 mA.

- Pete

Knowing Sansui manuals like I do I am not sure that is a misprint. The outputs start to warm up when set to 50MA on the 9090, I set both the 8080 and 9090 to 30MA. Justs seems to work better and stays much cooler.

zenith2134
01-27-2008, 10:11 PM
Anyone have the 2000x readily available? I don't wanna seem greedy, but I'd love to make sure everything's up to spec on mine.

Windwalker
01-28-2008, 01:33 AM
Anyone have the 2000x readily available? I don't wanna seem greedy, but I'd love to make sure everything's up to spec on mine.

Yea what he said, except make it a 4000. PLEASE

jpdylon
02-07-2008, 11:20 AM
If you have a sansui 5000, 5000a, or early 5000x that uses the F1040 or F-1040-1 boards, this thread will instruct you on how to upgrade the bias devices so that the machine can operate safely.

A big thanks to Johncan for sending me the 5000a for the subject of this thread.


You will need:

solder wick
solder (64/40 is good)
good 50 watt solder station
120 watt soldering gun
various sizes of needle nose pliers
surgical forceps are a plus
#2 and #1 Phillips screw drivers.
non-conductive epoxy
(4) NTE-605a or STV-2h diodes.
22ga wire
100pf capacitor
(2) 2sc2240 or 2sc631
shrink tubing
exacto knife
mixing stick (for the epoxy)
2 jumpers with alligator clips
150 ohm 2 watt resistor
A variac is nice too.


Let's begin!

Start by taking it out of the case and removing the top cover and bottom covers. bleed down the power supply caps with the 150 ohm resistor to the chassis. Pull out the amp fuses so any residual energy does not get to the driver board.

Here is what the F-1040-1 boards look like in the 5000a
http://www.audiokarma.org/forums/attachment.php?attachmentid=77977&stc=1&d=1202404687[IMG] [IMG]http://www.audiokarma.org/forums/attachment.php?attachmentid=77978&stc=1&d=1202404687

The problem lies with the thermal feedback diodes. They are the big black square things. They will open, causing full forward bias to be put on the output transistors. This is about 800mv, which saturates the outputs and kills them. WHen that happens it will destroy most of the components on the driver board. If that happens, its best to find a new board. They never really can be successfully repaired.

jpdylon
02-07-2008, 11:25 AM
Don't try to work on the driver boards with them installed in the chassis. its a headache and will only cause you troubles. They MUST be removed from the chassis if your repair is to be a success.
http://www.audiokarma.org/forums/attachment.php?attachmentid=78011&stc=1&d=1202406915

There are 8 leads to unsolder per board. Rail, output cap, 2 ground straps, 2 protector leads, and two input leads. Note their locations. You'll need a soldering gun to remove the ground straps.
http://www.audiokarma.org/forums/attachment.php?attachmentid=77980&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77981&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77982&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77983&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77984&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77985&stc=1&d=1202405056

jpdylon
02-07-2008, 11:29 AM
Now that you have the leads unsoldered, its time to take the amplifier out to work on it. The entire assembly can come out including the output transistors and heatsinks. This saves time unsoldering the output transistors.

Remove the back panel covering the heatsinks, then unscrew the heatsinks and the screws that hold the driver board in. It will all come out as one piece.
http://www.audiokarma.org/forums/attachment.php?attachmentid=77986&stc=1&d=1202405304
http://www.audiokarma.org/forums/attachment.php?attachmentid=77987&stc=1&d=1202405304
http://www.audiokarma.org/forums/attachment.php?attachmentid=77988&stc=1&d=1202405304
http://www.audiokarma.org/forums/attachment.php?attachmentid=77989&stc=1&d=1202405304
http://www.audiokarma.org/forums/attachment.php?attachmentid=77990&stc=1&d=1202405405

jpdylon
02-07-2008, 11:33 AM
Now that the board is out you can get a better look at what you're up against. The old devices will come out easily enough, but now you will need to adapt the new devices.

The devices we will use are the NTE605a or the STV-2h. They are dwarfs compared to the originals, but they can be adapted to work.

http://www.audiokarma.org/forums/attachment.php?attachmentid=77991&stc=1&d=1202405561
http://www.audiokarma.org/forums/attachment.php?attachmentid=77992&stc=1&d=1202405561
http://www.audiokarma.org/forums/attachment.php?attachmentid=77993&stc=1&d=1202405561
http://www.audiokarma.org/forums/attachment.php?attachmentid=77994&stc=1&d=1202405561
http://www.audiokarma.org/forums/attachment.php?attachmentid=77995&stc=1&d=1202405561

jpdylon
02-07-2008, 11:39 AM
With your new devices prepared, check to see if they will install. You may need to attach wire to the ends of the device for it to reach the 2sa485 pre-driver transistor if your leads aren't long enough.

I also place shrink tubing over the leads so that no electrical current can touch any other device.

http://www.audiokarma.org/forums/attachment.php?attachmentid=78000&stc=1&d=1202405817
http://www.audiokarma.org/forums/attachment.php?attachmentid=78001&stc=1&d=1202405817
http://www.audiokarma.org/forums/attachment.php?attachmentid=78002&stc=1&d=1202405817
http://www.audiokarma.org/forums/attachment.php?attachmentid=78003&stc=1&d=1202405817
http://www.audiokarma.org/forums/attachment.php?attachmentid=78004&stc=1&d=1202405817

DO NOT SOLDER THEM IN UNTIL THE EPOXY HAS SET. This can take anywhere from 15 mins to a half hour depending on what you use. YOu will need to make sure the new devices contact the body while the epoxy is drying.

jpdylon
02-07-2008, 11:54 AM
More shots of the new devices mounted up and epoxied in palce:
http://www.audiokarma.org/forums/attachment.php?attachmentid=78005&stc=1&d=1202406077

Once you've made sure the epoxy has set, you can solder in the new diodes. DOUBLE CHECK TO MAKE SURE YOUR POLARITY IS CORRECT.

You also want to solder them in as quickly as possible. I would take a 30 second break between leads. If you overheat the new devices they will fail and your work will be a waste.
http://www.audiokarma.org/forums/attachment.php?attachmentid=78006&stc=1&d=1202406077


Also compensate the 2SC485 with a 100pf 100v capacitor between the collector and base. This gets rid of a small oscillation that will occur at higher frequencies, and is absolutely critical if you have to replace the pre-driver transistors. On some boards there is actually a provision for this labeled c810.
http://www.audiokarma.org/forums/attachment.php?attachmentid=78007&stc=1&d=1202406077

While you're in here, look at the initial audio amp transistor near the input leads of the board. if its a 2sc458 REPLACE IT. These transistors are notorious for becoming noisy and opening. This will cause all sorts of pink noise and crackling. Replace it with a 2sc631 or 2sc2240. I prefer the later for its low noise and low leakage characteristics.
http://www.audiokarma.org/forums/attachment.php?attachmentid=78008&stc=1&d=1202406077


And there you have it!

That is what is required to update the F-1040 series boards so that they operate safely. Again, if the amp has blown out, just find another board. The success rate at which the board can successfully be repaired and reliably work again is very low.

Hopefully this will be of use to the folks who have the skill to perform this task. This is NOT for the novice. Try it out on a 5000 series you don't care about, or have a parts unit standing by in case of a failure. If you install the diodes backwards or overheat them, the amp will self destruct when you power up.

After the installation, the old bias procedure is no longer valid. measure between the emitter (blue lead towards the bottom at the back of the driver board) on the final output device and ground. Adjust VR-02 for 12mv adjust again after 15 mins. I will use a variac to slowly power up and monitor bias one channel at a time.

jpdylon
02-07-2008, 11:56 AM
All done!, post away!!! :D


Hey Paul, could you please make this a sticky?

Sansui Louie
02-07-2008, 01:27 PM
Sticky! Sticky! Sticky!

xoaphexox
02-07-2008, 06:37 PM
Holy smokes that is a lot of work. Makes you really appreciate modular designs like the AU-9500 even more!

Good work. Thanks for taking the time. Nothing like a good picture-walkthrough thread!

Johncan
02-07-2008, 07:17 PM
Holy cow!!!!! I had no idea it involved so much. That is an absolutely amazing pictorial.

You are the man!

Thanks!

KingBubba
02-07-2008, 07:32 PM
I knew there was a reason I decided to not buy that 5000a that I saw at the flea market a while back. :D

BrandXRC
02-07-2008, 07:33 PM
Thanks, Jordan, for taking the time to document this procedure for us, it was very informative, and easy to read and understand. :thmbsp:

LBPete
02-08-2008, 09:22 PM
Thanks Jordan. Very well done. Should be a sticky.

- Pete

nosirrah
02-09-2008, 12:31 AM
Nice work Jordan, and I agree, it should become a sticky.
Did this mod apply to the 5000X model?
I always thought the issue was solved by Sansui with the 5000X.:scratch2:
Casey

jpdylon
02-09-2008, 12:41 AM
No, actually some early 5000x models have the 1040-1 boards believe it or not. There are very few of them, but they exist.

Sansui lost a TON of money when it came to repairing these. Anyone who was a sansui authorized service center at the time probably had a ton of work on their hands.

xoaphexox
02-09-2008, 06:59 AM
So by "retrofit" do you mean the earlier models of the 5000 series did not have the problem and it was the later ones that did?

LBPete
02-09-2008, 10:23 AM
The 5000, 5000A and very early production 5000X models were originally built with the F1040 boards. These boards all had the inherent problem Jordan described and were prone to failure. The permenent countermeasure Sansui developed was a redesgned board, the F-6013. The later production 5000X were built with the F6013 boards.

Many, Many 5000s and 5000As had the 6013 boards installed for free under warranty. Sansui continued to offer this free upgrade to 5000 owners up thruough the early 1980s, 10 to 12 years after these units were originally produced. How's that for a warranty?

So the only way to know what boards are in your 5000, 5000A or 5000X is to open them up and look. If they have the 1040 board, consider doing Jordan's modification. If they have the 6013 board, Rock On.

- Pete

jpdylon
02-09-2008, 10:35 AM
no, the 5000 and 5000a have the problem almost guaranteed unless they were sent back to sansui for the 6013 boards.

Early production lines of the 5000x have the 1040 board too, however by mid 72' they were all F-6013 boards

The real way to find out if you have the problem is to pop the top on your machine. If it has a 1040 board, look for the black square things sitting atop o f the T0-39 pre drivers --you can't miss them.

There are moron techs out there who simply put 1n4004 diodes on the board just to make it work again. If you see a 1040 board without anything sitting on the pre driver transistors FIX IT PRONTO!

In lamen's terms The whole purpose of the setup is to regulate bias current with the varying heat conditions of the pre driver stage. As the amp heats up from playing it loud, the bias will creep up. Without any regulation the bias would keep going up even after you turn the volume down. Eventually the transistors would go into a thermal runaway state and fry.
The device is a temperature compensating dual-forwarding diode. Standing alone, it reads as two diodes would be in series. However as it heats up, the voltage drop across the diode goes down. When in circuit, this effectively lowers the bias automatically as the amp heats up.

You can still overheat the amp if you play it at crazy volumes on a 4 ohm load, but when you cut the music, the heatsink will cool because it backs off the bias instead of remaining hot or getting hotter!

I hope the explanation is helpful. I'm terrible at trying to explain these things, I understand it completely in my head, but have a hard time trying to convey what's in my head to others.

LBPete
02-09-2008, 10:46 AM
Jordan, I'm going to argue that any original 1040 boards that are still in service have passed the test of time and MAY be OK if used sanely or is a rarely used collector piece. All bets are off if the board has been modified. But if you are going to use the receiver on a regular basis. Then the upgrade should be done.

- Pete

jpdylon
02-09-2008, 11:07 AM
Its a possibility that less use may contribute longevity to the original 1040 boards.

However, the company who made the diodes, Origin had poor quality control. There was another instance of diodes from these manufacturers failing even at early age. The 3000 and 3000a used origin diodes in the bias regulation circuit. They would open and the same thing would happen to the 3000/a
Except that since the 3000 series had driver transformers and output directly coupled to the speakers when the outputs died so did the speakers.
Sansui provided a service bulletin and offered free upgrades to add output capacitors to block the DC that would kill the speakers as well as changing the diodes. Fred Longworth was servicing the 1040 boards for sansui back when this was really a problem, and he has told me they were failing as early as a couple of years after purchase.

Another recent example was an old kenwood piece from the late 60s that someone brought me for repair. The power supply rectifier was open, and it was also made by 'origin'

I'm convinced these diodes are doomed to fail. Its not a question of IF they will fail, its when. Being that they are located in a very crucial part of the amplifier, a failure of the diodes will take out the amplifier. They go down HARD and its near impossible to repair the boards completely -especially if they have been charred by fire from burning resistors. Then you have to find a new board and upgrade it.

I would rather be safe than sorry. I've literally worked on about 18 of these machines. At least 6 out of that amount had open diodes and blown amps. To me it would be silly to leave it alone and continue to use it - even if its just on an occasional basis.

Your mileage may vary.

Snowbum
02-23-2008, 02:02 PM
I was intrigued by Jordan's efforts here. My company was a Sansui Warranty Station for many years. I still have in storage (I am nearly retired) tons of all sorts of Sansui manuals, my 5000 series fat folder...and...a BOX on my shop floor in the corner...full of changed F1040 (and -1) type boards. Probably still have plenty of 2SC1111...and, especially the better 2SC1116A output transistors, ETC.....and did so many conversions on the various 5000 units I could not possibly count them all. I have not done one in about two years now. It is true that 5000, 5000A, and even the 5000X had faulty 1040 series boards boards...until the F1063 boards came out. Those boards were initiated into final production. In my opinion, Jordan is correct in what he has posted, but changing the diode may, in some cases, not fix the bias runaway problem...the 1063 had other improvements, and were quite stable, overall. That the input transistor gets noisy and should be replaced, and the anti-parasitic capacitor added, yes, I agree.
UNfortunately, Sansui stopped giving us Warranty Stations free 1063 boards and output transistors;...let alone paying for the labor...around 1982. I did a number of conversions after that with left-over boards, but Sansui did not supply the output transistors, hence my stock of 2SC1166A. Many of you undoubtedly also remember that Sansui had modification kits for the 3000, not just the 5000.
I got to be pretty quick at modifying the Sansui 5000 models, after doing about a dozen....I probably have done a hundred or more. Kinda doubt I will see any more around here. Eventually all this stuff is going on Ebay, maybe anyway.
Robert

Snowbum
03-03-2008, 12:09 PM
Just a final word on this. The MAIN problem with the original 1040 boards, and the 1040-1 boards, was, yes, the thermal runaway, and, yes, it was due to faulty dual-diodes...accurately said by JPDYLON. However, the boards are SOMEwhat unstable under SOME circumstances of types of loads (esp. electrostatic speakers, which 'look' like capacitors) and thermal conditions too. Thus the rather heavily revised F6013 boards. In MY opinion, if the diodes on the original F1040 and F1040-1 boards are still working OK, then they are more likely to continue that way than not. You take a chance, but it is a good chance. If anyone needs the output transistors, etc., I still have some, if yours are burnt.

markallen
03-03-2008, 03:20 PM
Thanks to JPDYLON for putting this together, and to those who contributed. Well done, and very interesting to me as an owner of a 5000A. Mine has the F-1040 boards, so they look a little different than the ones pictured, but the mod is the same, I believe.

Is the STV-2H a straight-across equivalent for the NTE-605A? Is it installed in the exact same fashion? I have read on related threads here on AK that the NTE-605A is basically impossible to get anymore.

Where is the best place to obtain either of these diodes? If possible, the thing I'd LIKE to avoid is having to pad an order to reach a minimum, or pay a high minimum shipping price just to get these few small (probably inexpensive) parts - or do I ask too much?

jpdylon
03-04-2008, 12:19 AM
the stv-2h and 605a are pretty much the same. they are mounted the same.

You'll have to search a bit for the 605. i would talk to electronics places that were nte dealers and see if they have a stock of them somewhere.

last time i checked consolidated electronics had the stv-2h devices.

jordanch68
03-04-2008, 08:43 AM
Thanks LBPete, now maybe I can fix my 5050 that I posted about back in 2005. :)

eradoncic
03-08-2008, 03:16 AM
Here's my contribution for AU-X701/901

cpmschd
03-10-2008, 01:12 AM
Bias and DC offset... some AU-717 images attached...

JF

LBPete
04-13-2008, 11:32 AM
Here is the offset and bias adjustments for the G 5000 and G 4700.

Enjoy,

- Pete

Morden2004
04-14-2008, 06:00 AM
Thanks, Pete and all the others who are adding to this thread!

This thread my prove to be one of the best for technical assistance.

Paul

jimbofish
04-14-2008, 10:04 PM
Here is the offset and bias adjustments for the G 5000 and G 4700.

Enjoy,

- Pete

I just used the info to adjust my G-5000. Thanks very much. :thmbsp:

Maybe it's just me or my unit, but I think there might be an error in the pdf. I tried to adjust the bias as described, but there was no change on either channel. I then used TP 78 & 40 to set the Left channel, instead of the right and it worked. TPs 77 & 39 worked for the Right channel. To be perfectly clear, I wasn't able to see any markings to confirm that VR06 was actually on the right side of the board with VR04 & VR02 and vice versa with VR05 on the left side with VR03 & VR01. It doesn't seem likely that the bias pots would be on opposite sides from the offset pots.

Maybe someone else can confirm this or show me where I went wrong. :scratch2:

LBPete
04-14-2008, 11:52 PM
It's not unusual for Sansui manuals to be dyslectic.

- Pete

markallen
04-16-2008, 05:48 PM
the stv-2h and 605a are pretty much the same. they are mounted the same.

You'll have to search a bit for the 605. i would talk to electronics places that were nte dealers and see if they have a stock of them somewhere.

last time i checked consolidated electronics had the stv-2h devices.

An update on availability of the STV-2H: I tried to order some today, and the (very nice) guy at Consolidated who I talked to said he's sold hundreds - but they're all gone now!

If anyone knows where either the STV-2H or the NTE 605A can be obtained, can you let us in on it? Thanks.

russ1965
04-19-2008, 11:27 PM
Good Post Jordan. I finally got a chance to look at my 5000Xs. It has the F-1040-1 boards in it but the board has two sets of two diodes in series on the botton of the board, HEP 170 is printed on the four diodes, no themoral connections. The two SA485 have a heat sheild that looks homemade, a circle of sheet metal around the transisitor and strap from the circle that exttends a 1/4 inch up and then across the top. The boards have the c458 transitor.

The Question should these be changed.

Thanks
Bob

jpdylon
04-20-2008, 10:37 AM
Sounds like a very interesting, but incorrectly done mod.

The person used two diodes in series to compensate for the fact that the original devices were dual-junction. That much he knew. However, the those types of diodes are probably not designed to change value with temperature - and that's where the problem is.

If there is no thermal feedback from those devices, then there is no way the bias gets backed off when the amp heats up. This will eventually end up in a thermal runaway condition and the output transistors will die.

The heat shield looking thing on the 2sa485 used to be the hardware that attached the original diode devices. They were epoxied to the tops of the transistors and can be difficult to get off without pulling the board and chipping the epoxy away.

The 2sc458 should be replaced. Its really a crummy transistor.

If it were me, I would pull the diode mess out and put correct devices in described in the retrofit thread.

russ1965
04-21-2008, 01:36 AM
Thanks for the reply. That's what I thought. The way the four diodes sets were made cripped at the series connection then soldered, each set the same, and the put in the exact same position, it looked like it came from the factory that. This one goes under my bench, the dining room table, since it is working fine except for famous 8.3v 150ma indicator light which is dead.

Thanks
Bob

Fast_Eddie
04-21-2008, 09:49 AM
Wow, great write up and pics. I did my 5000a and it works great, but you did a much, much better job. I can say, it is possible to do the job without taking the boards out, but your job is much better. In fact, I may re-do mine someday.

Take care,

Ed

Morden2004
04-24-2008, 07:50 AM
because this is such an important DIY thread and because at least one member asked :D, I have made this thread a 'sticky'. :thmbsp:

Enjoy!

Paul

KlausDK
05-03-2008, 05:14 PM
Here is the bias adjustments for the AU-9900A/11000A.

BRgds Klaus

avguytx
05-03-2008, 05:30 PM
Here is the bias adjustments for the AU-9900A/11000A.

BRgds Klaus

And that joker is one pain in the a$$ to adjust! I still haven't gotten around to doing mine.

KlausDK
05-14-2008, 02:34 PM
Here is the bias adjustments for the AU-20000.

BRgds Klaus

dread31
06-05-2008, 01:37 AM
Anyone have the 2000x readily available? I don't wanna seem greedy, but I'd love to make sure everything's up to spec on mine.


Me too. I have a 2000x on the bench as we speak. I'd really appreciate all of the help I can get.:yes:

Dave

ZebraBlvd
06-05-2008, 06:52 AM
I have made this thread a 'sticky thread' so that we can always access this terrific list of parts suppliers. Thanks to all who contributed to this list.

Paul

Your a good man, Paul. You know a great value when you see one. :yes: I thank you as I know many others will in the future. And thanks also to those that have already contributed. This will make it a lot easier for us weekend solderers.

LBPete
06-10-2008, 12:34 AM
Here is the DC offset and Bias current adjustments for the QRX-7500. There is also a page with the regulated power supply and meter adjustments. Thanks to AK member kbs48 for the scans!

- Pete

poochar
06-10-2008, 11:02 AM
Hello ....
Does anyone have the procedure for the AU-417: Bias Current and DC Offset?

Thanks,
Eric

fyrrwulf
06-20-2008, 11:45 AM
I see the procedure for the AU-9900A/11000A, but not for the AU-9900/11000. Anyone out there have the procedure for it? Would be much, much appreciated.

rush2112guy
07-12-2008, 12:23 AM
I was intrigued by Jordan's efforts here. My company was a Sansui Warranty Station for many years. I still have in storage (I am nearly retired) tons of all sorts of Sansui manuals, my 5000 series fat folder...and...a BOX on my shop floor in the corner...full of changed F1040 (and -1) type boards. Probably still have plenty of 2SC1111...and, especially the better 2SC1116A output transistors, ETC.....and did so many conversions on the various 5000 units I could not possibly count them all. I have not done one in about two years now. It is true that 5000, 5000A, and even the 5000X had faulty 1040 series boards boards...until the F1063 boards came out. Those boards were initiated into final production. In my opinion, Jordan is correct in what he has posted, but changing the diode may, in some cases, not fix the bias runaway problem...the 1063 had other improvements, and were quite stable, overall. That the input transistor gets noisy and should be replaced, and the anti-parasitic capacitor added, yes, I agree.
UNfortunately, Sansui stopped giving us Warranty Stations free 1063 boards and output transistors;...let alone paying for the labor...around 1982. I did a number of conversions after that with left-over boards, but Sansui did not supply the output transistors, hence my stock of 2SC1166A. Many of you undoubtedly also remember that Sansui had modification kits for the 3000, not just the 5000.
I got to be pretty quick at modifying the Sansui 5000 models, after doing about a dozen....I probably have done a hundred or more. Kinda doubt I will see any more around here. Eventually all this stuff is going on Ebay, maybe anyway.
Robert
Feel like doing one more 5000A?

AKE13
07-13-2008, 01:21 AM
JPDYLON, nice professional job. Does thi apply to 5000 too? I came across to this thread, since I have a BA-5000 with one channel out problem.......any experience / suggestion? Regards

terra1
07-23-2008, 01:11 PM
Scans from Sansui 4000 Service Manual
Current Adjustment
Output Adjustment
Protector Adjustment

Current
F001, F002
VR803, VR804
VR701, VR702

Output
VR801, VR802

Protector
VR901, VR902
VR703, VR704
VR701, VR702
L012

I find it confusing though. Found VR803 but couldn't find trimmers VR701, VR702?
And VR901, VR902 are under the bottom cover.

charmingman
08-01-2008, 01:47 PM
Hi, the link to G4700 in the first post here is not working.

Any help?

thanks, Jay

LBPete
08-01-2008, 11:57 PM
Try again. I reloaded the link. You can also get it in post 27 of this thread.

- Pete

LBPete
08-02-2008, 12:22 AM
Thank you to Klaus and terra1 for the new procedures.

- Pete

charmingman
08-02-2008, 12:27 AM
Hi Pete, thanks for your efforts, but still no go for me.

If I click on either 4700 link (posts 1 & 27) I get to a dead end log-in page that refuses me even though I'm already logged in. If I right click on the 4700 links I am presented with an item to download called "attachment.htm". I don't think it's my error as I can access the other pdf files in posts 1 and 27, just not the 4700 one. Typical computer behavior!

cheers, Jay

terra1
08-02-2008, 01:14 AM
Hi Pete, thanks for your efforts, but still no go for me.

If I click on either 4700 link (posts 1 & 27) I get to a dead end log-in page that refuses me even though I'm already logged in. If I right click on the 4700 links I am presented with an item to download called "attachment.htm". I don't think it's my error as I can access the other pdf files in posts 1 and 27, just not the 4700 one. Typical computer behavior!

cheers, Jay

I was able to click both posts 1 & 27 and downloaded no problem. Maybe you need to clear your temp files, cache or empty your trash. I use Firefox browser.

But I'll attach a jpg of the section. Hopefully it won't be resized too much where it's too blurry to read.

This is for G4700. It is just a little snippet of the page so it isn't a very large file at all.

You may need to move your cursor over the picture when it opens and click it to enlarge to normal size.

charmingman
08-02-2008, 02:56 AM
Hi, thanks for your continued assistance.
I continue to have this weird trouble.
When logged in I can see the thumbnail image of the file on your last post, but I have the same problem as stated above, left click takes me to a refusing log-in page, download attempt gets me "attachment.htm"
Of course the similar appearing attachment on post 38 works just fine for me, as do the other pdf files. Therefore I doubt it's my browser.

Could it be a file access permission issue?

Can other members get to the 4700 pdf on 1 & 27 or the jpg in the post above?

Does our moderator sort out such glitches?

And why is it the only file I want to see is also the only file I can't see?

thanks, Jay

charmingman
08-02-2008, 11:39 AM
Oh, never mind, today all the files work for me, including the ones I want. What the hell was going on?

thanks, Jay

jblmar
08-05-2008, 11:14 AM
Would you have a copy of the service manual? I'll check the boards over the weekend.

Ron

jblmar
08-06-2008, 01:15 PM
Don't try to work on the driver boards with them installed in the chassis. its a headache and will only cause you troubles. They MUST be removed from the chassis if your repair is to be a success.
http://www.audiokarma.org/forums/attachment.php?attachmentid=78011&stc=1&d=1202406915

There are 8 leads to unsolder per board. Rail, output cap, 2 ground straps, 2 protector leads, and two input leads. Note their locations. You'll need a soldering gun to remove the ground straps.
http://www.audiokarma.org/forums/attachment.php?attachmentid=77980&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77981&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77982&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77983&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77984&stc=1&d=1202405056
http://www.audiokarma.org/forums/attachment.php?attachmentid=77985&stc=1&d=1202405056

Nice work!!
Great photos.
One question. Instead of the solder gun, why not drop the 2 capacitors next to the amplifier boards? You'll have a clear view of the solder side of the board to work on.

Ron

jpdylon
08-06-2008, 09:25 PM
Its a little more difficult to get a tool in there to loosen the clamp. I found it easier and less time consuming to unsolder the ground rather than dropping the caps down.

Your mileage may vary.

mplsbob
08-11-2008, 02:48 AM
Hope this works, attaching a PDF page from the manual

jblmar
08-11-2008, 09:33 AM
I'm in the process of working on a fellow AK members 5000A.
Removing 4 screws allows easy access to the foil side of the 1040 boards for safe desoldeing/soldering.
Moving the 2 large capacitors offers enough space to allow the solder iron(s) to be used safely.
Do the same for the caps to the other channel.

Ron

olafi
08-20-2008, 02:41 PM
http://www.hndme.com/productcart/pc/viewCat.asp

Susurus
08-30-2008, 06:10 AM
Here's adjustments for a AU-X1 (http://www.classicsansui.net/images/Schematics/sansui%20au-x1%20service%20manual%2012.jpg)

I know I'm among much more knowledgeable people here, so bear with me thanks.
Yes I did read the EW sticky thread, and absorbed some of it.
------------

4-1 steps 1-4; PS Voltage adj.

Access F-2778 from inside a long thin flat panel just behind the front plate, top side. (Lotsa glue on this board.)
The four metal contact tabs (TP01, TP02, TP03, TP04) are evenly spaced along it. Nearby each one are the four VR01-VR04 trim pots.

http://www.audiokarma.org/forums/attachment.php?attachmentid=106249&d=1220098990

There's dyslexia in the manual (or it's an earlier/later model variation). One of my channels is out in the preamp section, (GRD - TP03 gives .95V, won't adjust) but the power amp plays both R&L through the Pre-Ins. Hooray!

------------
4-2. step 1-2. Speaker Terminal adj.

F-2775 driver circuits. VR01 is the blue pot near the top, easy to reach. VR02 is the one farther in.

http://www.audiokarma.org/forums/attachment.php?attachmentid=106254&d=1220097555

------------
4-2. step 3 (Left channel)

Uh oh. Now I'm in trouble...
Manual says to adjust for DC 25 mV +-1 mV, measure "Between emitter of power transistors, TR701 & TR03 (between T.P Pin)."

I'm gonna need to do some googling here to know where to connect to get the right reading.

There are 6 Sanken transistors per side;
three 75C2498 (7SC?) and three 9N0 2SA1068.

http://www.audiokarma.org/forums/attachment.php?attachmentid=106251&d=1220095925 . http://www.audiokarma.org/forums/attachment.php?attachmentid=106255&d=1220095960

GRD and between the resistor and the '1068 right-most side Left Channel transistor, I can adjust easily from zero to 25 mV. It was way unbalanced, and one channel's heat sinks were heating up pretty hot while the other was ice. But I'm getting ahead of myself to section 4-3.

This is an evolving thread--probably get moved once it's done, and just leave a link here in the sticky thread.

-------------
Meanwhile, some pics for fun:

http://www.audiokarma.org/forums/attachment.php?attachmentid=106248&d=1220095925


More pics as I get farther along this journey...

http://www.audiokarma.org/forums/attachment.php?attachmentid=106261&d=1220099861


.

LBPete
08-30-2008, 02:59 PM
Thanks, Susurus! That's a very nice tutorial. I know how long it takes to put something like that together and appreciate your effort. Now, if I only had an AU-X1. :scratch2:

- Pete

alexandru
09-24-2008, 03:07 PM
Here are the settings for 771 (http://www.audiokarma.org/forums/showthread.php?t=185044)

Susurus
09-25-2008, 08:28 PM
one day, a stereo in every room, maybe two


She wishes I only had two in every room! :wave:

nosirrah
10-02-2008, 10:47 PM
CDFixer
Number 1 USC Trojan Fan
Join Date: Jan 2004
Location: Orange County Ca
Posts: 1,273

Here are all the differences that I know of in the two receivers

Tone and filter circuits, Identical on 8080/8080DB and 9090/9090DB, the 9090/9090DB versions have crossover selection switches on the tone board that the 8080/8080DB series do not have.

Dolby circuit only on the 8080/9090DB

Speaker selection 8080/9090 places the speakers in Parallel in A+B and A+C, the 8080/9090DB places them in series.

Tuner the 9090 has a noise canceller/multipath circuit incorporated in the tuner. the 8080 and 8080/9090DB receivers do not.

The 8080/9090 tuner lights are on only when the tuner is selected the 8080/9090DB they are on all the time. (Note the 8080/9090 can be modified to do this)

The 8080/9090 has one phono input, the 8080/9090DB has two.

The Amp section on the 8080/9090DBs is more robust, using a standard NPN/PNP complementary Push/pull amplifier. The 8080/9090 use a quasi complementary NPN only amplifier

The power supply on the 8080/9090DB is larger and has a much higher current capability. The filter caps on the 8080/9090 are 6700UF on the 8080/9090DB they are 12000UF.

The 8080/9090DB have two pre-out jacks, the 8080/9090 only one.
__________________
Cheers Jim

"Experience is a hard teacher because she gives the test first, the lesson afterwards." -- Unknown

Tichu
10-04-2008, 01:35 PM
Hi,

I just repaired and cleaned a nice G-9700 receiver.
Everything works, need just a final adjustment.
I got a PDF of the service manual, but the adjustment section has a a typo: it says "DC +/-5mV" for the BIAS value ...

Anyone knows what the correct value should be ?

LBPete
10-05-2008, 11:29 AM
Hi Tichu, welcome to AudioKarma. The G-9700 is a powerhouse receiver well worth the time and effort to restore. The service manual is a little vague about the bias setting. The consensus is to set them to 5mv. They have a poor temperature compensation circuit and it's important to keep them running cool.

- Pete

Tichu
10-05-2008, 11:50 AM
Hi Tichu, welcome to AudioKarma. The G-9700 is a powerhouse receiver well worth the time and effort to restore. The service manual is a little vague about the bias setting. The consensus is to set them to 5mv. They have a poor temperature compensation circuit and it's important to keep them running cool.

- Pete

Thanks for your reply :)

Hmm, 5mV seems very low. The voltage is measured across complementary emitters, with 0,330 Ohms resistors.

I also checked manuals for G-9000 and G-7700: G-9000 says 5V: probably another typo.
The G-7700 is more serious at 16mV +/- 1mV.
I also read in a post on AK that 50mAis recommended for 9090, and 30mA for 8080.

So I mixed these informations, and did some maths: 16mV across 2x 0,330 Ohm is ~25mAmp. Since there are 2 pairs of transisors per channel, it comes to 50mA BIAS current for each channel: spot on the 9090 recommended value.
So I set my receiver to 16mV, and my G-9700 runs cool. So I am ...
.

LBPete
10-08-2008, 12:51 AM
Tichu, I was looking at the G-9700 schematic tonight and it has a very clear call out of 5mV showing a measurement accross the emitter resistors. No ambiguity here.

Here is a scan of that part of the schematic.

- Pete

Hyperion
10-14-2008, 11:26 AM
And some for UK based enthusiasts...

http://uk.rs-online.com/web/ transistors, semis, just about everything else
http://uk.farnell.com/ transistors, semis, just about everything else
http://www.hificollective.co.uk/ transistors, semis, passives etc
http://sellweb.co.uk/ transistors, semis, passives etc

There must be more in the UK - I have personal experience of the top 3 - very good service.

John

mokfo
10-17-2008, 05:10 AM
Hi.. Im new to this site... could anybody help me on the procedure for adjusting the biases for AU-G77X amp. TIA.

LBPete
10-19-2008, 12:55 PM
Hi Mokfo,
Welcome to AudioKarma. Here is the bias and offset procedure for the AU-G77X. There are two pages in this file. I hope it is useful.

- Pete

LBPete
10-19-2008, 01:01 PM
To finish the discussion on the G-9700, here is the procedure from the service manual. The recomended bias value is 5mv. This procedure applies to the G-9700, G-971, G-8700DB and G-871DB. There are seperate illustrations for the G-9700/971 and the G-8700/871

- Pete

Tichu
10-27-2008, 08:26 AM
Pete,

Thanks, but I already have these pages, and in fact my original question was about the missing exact value for BIAS: you can read yourself that there is only a tolerance (+/- 5mv), and no actual value.
This is why I think it is a typo: I cannot seriously believe a BIAS at DC 0V is normal ...

LBPete
10-28-2008, 12:44 AM
Take a look at post 54. That's a scan from the schematic that shows the bias measurement as 5 mv. I agree the spec in the adjustment section is a little ambiguous but what's shown on the schematic looks like they mean it.

Also, the concenses of the experienced techs here is to set it to 5mv. These receivers have shitty temperature compensation in the bias circuit and are prone to thermal runaway. Setting the bias low, 5mv, helps prevent that.

- Pete

Bill Ford
11-04-2008, 02:17 PM
qrx-7001 does someone bias speck for the driver boards?I just checked all 4 channels and there set around 36ma.Thank you Bill Ford.

ecluser
11-13-2008, 03:43 PM
See post #6 of this thread:


http://www.audiokarma.org/forums/showthread.php?t=192583

mungo911
11-22-2008, 10:48 AM
Hello everyone. I just got a 5000a from a friend who had it in storage for 20 years or so and wish I had found this thread and site before I fired it up! Initially, when I hooked up the speakers and ant, nothing happened; the 4A fuses were missing. I put them in, turned it on and had sound! 3 seconds later, POOF and smoke and the left channel was gone. Cooked a number of components (that are obvious) on the driver board, F-1040-1 type. I am worse than a complete novice at this so please bear with me. Anything I know about this unit is from reading this forum. The boards in my unit, both 1040-1, do not look the same as in the pics. There are no black ugly things on either board. There are some diodes, some connected in series (end to end) near them making me think someone may have already messed with them in the past. I have attached pics of the bad board and modifications. My questions are...
1. Can F6013 driver boards be found ?
2. At what price?
3. Is it really worth the time, effort and expense?
4. If not, is there anything worth salvaging from the corpse?
Thanks in advance for any input.

Jerry

jpdylon
11-22-2008, 11:05 AM
You can cannibalize 6013 boards from late production 5000x machines and sometimes they will pop up on ebay - though rare.

Not sure about the price.

The 5000 series are a dime a dozen and are everywhere. Unless you're in love with this machine you can probably find another one cheap. Go for the 5000x with the 6013 boards. Pop the top to make sure.

There are parts on these machines that are usable in other 5000 series. The knobs and button covers are interchangeable with 2000a-5000 series models.

If it were me I would just part it. Save the wood case if it has it for another 5000 machine (if you plan to get one)

The diode mod there does not work. No thermal tracking for the bias. However unless one or more of those diodes opened or the bias pot opened - I don't think that mod would have cause it to blow that quickly.

mungo911
11-22-2008, 12:41 PM
Many thanks for your input. I appreciate it. Guess I'll look around for something else.

Jerry

PatA
11-23-2008, 07:29 PM
www.acme-sales.net - transistors (some hard to find) & semis, etc
www.ceitron.com - transistors (hard to find parts), semis, phono parts - fast service (about a week), original Sanken 2SA765's and Hitachi 2SC984's
www.partsexpress.com - various audio parts, speaker kits, etc
www.surplussales.com - crazy surplus parts
www.woodang.net - transistors (Genuine!) Sten from Sweden is great!
www.mcminone.com - Transistor & semis, etc
www.tritronicsinc.com - factory audio replacement parts
www.moyerelectronics.com - transistors, semis, etc
www.digikey.com - transistors, semis, just about everything else
www.mouser.com - on par with digikey

Always check out the minimum order fee for each company, usually around 25-30 bucks to avoid large handling fees!!

I emailed Sten at Woodang.net to ask him if he had a knob for my G-9000. He didn't but he sent me a link to a Euro seller that has a ton of different Sansui knobs. Here is the link; http://www.sansui-parts-shop.com/index.php?page=browse&action=list&orderby=DESCRIPTION&group=26&cat=17 Sten went out of his way to find me this and emailed back every time that I emailed him. Hard to find people like that any more.

Francisin88
12-08-2008, 11:01 AM
Hi There ....

Does anyone have the procedure for the AU-919: Bias Current and DC Offset?

Thanks, Francis

MrIgotNomoney
12-16-2008, 10:17 PM
Its a possibility that less use may contribute longevity to the original 1040 boards.

However, the company who made the diodes, Origin had poor quality control. There was another instance of diodes from these manufacturers failing even at early age. The 3000 and 3000a used origin diodes in the bias regulation circuit. They would open and the same thing would happen to the 3000/a
Except that since the 3000 series had driver transformers and output directly coupled to the speakers when the outputs died so did the speakers.
Sansui provided a service bulletin and offered free upgrades to add output capacitors to block the DC that would kill the speakers as well as changing the diodes. Fred Longworth was servicing the 1040 boards for sansui back when this was really a problem, and he has told me they were failing as early as a couple of years after purchase.

Another recent example was an old kenwood piece from the late 60s that someone brought me for repair. The power supply rectifier was open, and it was also made by 'origin'

I'm convinced these diodes are doomed to fail. Its not a question of IF they will fail, its when. Being that they are located in a very crucial part of the amplifier, a failure of the diodes will take out the amplifier. They go down HARD and its near impossible to repair the boards completely -especially if they have been charred by fire from burning resistors. Then you have to find a new board and upgrade it.

I would rather be safe than sorry. I've literally worked on about 18 of these machines. At least 6 out of that amount had open diodes and blown amps. To me it would be silly to leave it alone and continue to use it - even if its just on an occasional basis.

Your mileage may vary.

Guys Im reading this post. I have a Sansui 3000A that I have had for several years, It works fine.
After reading this post I pulled off the cover and I see several diodes on the back driver board.
Good sized doides with a blue band, should I be changinge these out ???
Time bombs ? This guy is about as clean as can be, and works like a champ.
I have been thinking about doing a cap job on it for quite a while, now Im wondering about the diode issue.
Origin diodes, is this a brand name ?

any comments ?

bob

cableguy2
12-22-2008, 11:52 AM
Wow, five pages and nobody has the procedure for the 6060. Man that is a hard one to find.

LBPete
12-22-2008, 11:55 PM
Check the 4th link on the first page. It links to the procedure for the 5050 and 6060.

- Pete

kretinus
01-21-2009, 09:32 PM
OK, what's the deal on the deviation between the schematic and reality on the 9090?

The pots on my driver board are not in the same locations as the schematics? Do I ignore the geography and go with the labeling?

Also, I need to pull the board and clean it, including the pots, what's the correct method for reinstalling and adjusting since the pots are probably not going to be in the ballpark afterall that? Do you mark the physical positions and hope it's in a safe range?

kdillinger
01-22-2009, 07:05 AM
I would suggest using a meter to measure th setting of the pots after you remove the board, before cleaning. Then after cleaning, setting the pots close to what you measured originally. Then finally tweak them in, using the recommended procedure with the board installed, under power.

Anyways, thats how I did it on my 8080DB.