View Full Version : Sansui Tech's come to my rescue PLEASE! G-7000


GENXVINTAGE
02-12-2009, 11:08 PM
Well lets start off by saying the receiver that is about to drive me to the funny farm is a G-7000. It powers on fine and the first relay clicks almost instantly and then after that NOTHING. No output anywhere. On FM it does NOT show signal strengh and wont attempt to find a station. Its just dead in the water. I can tell you what all I have checked or done so far but before I sound like a idiot has anyone had this problem before or any advise on were you would check first?? On the power supply board I did find a 10 ohm 2 watt resistor that was bad and replaced it and on the board that the selector switch attachs to (bottom side), I believe it is actually called the equalizer circuit board, I found 4 100 ohm resistors at the very end that were all bad and replaced them. Still the same result, nothing???

GENXVINTAGE
02-13-2009, 06:46 PM
Anyone?...... PLEASE?.......PRETTY PLEASE?

Tichu
02-14-2009, 06:48 AM
On the G-7000, there are 2 relays: the first one is for rush input current protection and clicks in quickly.
You should hear a second relay clicking after a few seconds to connect the speaker outputs. If you do not hear it, there maybe some problems in the power amp section: excessive voltage offset, or even shot output transistors.

For tuner problems, you may want to check the fuses (4 of them) and also the voltage on the tuner board.

GENXVINTAGE
02-14-2009, 06:24 PM
On the G-7000, there are 2 relays: the first one is for rush input current protection and clicks in quickly.
You should hear a second relay clicking after a few seconds to connect the speaker outputs. If you do not hear it, there maybe some problems in the power amp section: excessive voltage offset, or even shot output transistors.

For tuner problems, you may want to check the fuses (4 of them) and also the voltage on the tuner board.



Both relays are in good condition and I have tested all the output transistors and they are also fine?

terra1
02-14-2009, 06:38 PM
Don't miss tichu's comment about the fuses. good to replace them anyway they can look good with the filament intact but still be bad. If things are starting to fail, then fuses may be next to go anyway or at least you can eliminate those as cause.

Tichu
02-15-2009, 04:14 AM
GENXVINTAGE, you did not say if the second (speaker) relays clicks or not, just that is is in "good condition".

Excuse me if what I say seems obvious to you, but there are several reasons that could prevent this relay to connect the speakers:
- missing voltage in power supply section (check for glass fuses)
- DC voltage on amp output (maybe unadjusted offset, or pb with output transistors or driver board)
- overcurrent in output transistors (output transistor shot, or problem in driver board)
- problem in protection circuits
- any combination of above problems...

Fixing a vintage amp is (at least for me) a bit like being Sherlock Holmes studying the evidences and finding the solution that fits all facts.
So you need to find more facts (measure voltages, check parts) to help find the reason.

This is part of the fun and the pride to have a vintage high end gear that you fixed yourself !

GENXVINTAGE
02-18-2009, 01:18 AM
GENXVINTAGE, you did not say if the second (speaker) relays clicks or not, just that is is in "good condition".

Excuse me if what I say seems obvious to you, but there are several reasons that could prevent this relay to connect the speakers:
- missing voltage in power supply section (check for glass fuses)
- DC voltage on amp output (maybe unadjusted offset, or pb with output transistors or driver board)
- overcurrent in output transistors (output transistor shot, or problem in driver board)
- problem in protection circuits
- any combination of above problems...

Fixing a vintage amp is (at least for me) a bit like being Sherlock Holmes studying the evidences and finding the solution that fits all facts.
So you need to find more facts (measure voltages, check parts) to help find the reason.

This is part of the fun and the pride to have a vintage high end gear that you fixed yourself !

Second relay not clicking (replaced with a new one, same result)
All fuses have been checked
Every component on the driver board has been tested and it was recapped.
Output transistors all checked and are fine???

EchoWars
02-18-2009, 01:42 AM
People are trying to help you, and you're ignoring them.

-Check DC offset
-Check all regulated and unregulated power supply voltages

If these two items are beyond your abilities, you need to find someone who can do the work for you.

GENXVINTAGE
02-18-2009, 01:50 AM
People are trying to help you, and you're ignoring them.

-Check DC offset
-Check all regulated and unregulated power supply voltages

If these two items are beyond your abilities, you need to find someone who can do the work for you.

Sorry, didnt mean to ignore anybody. I am checking those now. Manual is a little hard to decipher.

Will I be able to get a correct reading on the DC OV without the second relay engaging?

EchoWars
02-18-2009, 04:27 AM
Depends on which side of the relay you try to measure from. If it isn't closing, then measuring from the output side is kind of a waste of time, don't you think? ;)

GENXVINTAGE
02-18-2009, 01:07 PM
Depends on which side of the relay you try to measure from. If it isn't closing, then measuring from the output side is kind of a waste of time, don't you think? ;)

YA Think? What I should have said is Im not sure were to measure from. I just found another bad transistor. Its a NTE F6 7YS. The manual shows a 2SF656. Any ideas on which one or what I can use there?

EchoWars
02-18-2009, 05:49 PM
The 2SF656 is a nonsensical number. Japanese gear bipolar transistors are 2SA, 2SB, 2SC, or 2SD.

Can't help you with where to measure offset, other than to say the relay contacts might be a good place if you can reach them, or the emitter resistors.

GENXVINTAGE
02-18-2009, 06:16 PM
The 2SF656 is a nonsensical number. Japanese gear bipolar transistors are 2SA, 2SB, 2SC, or 2SD.

Can't help you with where to measure offset, other than to say the relay contacts might be a good place if you can reach them, or the emitter resistors.

Its a SCR.

2SF656
Silicon Controlled Rectifier

V(DRM) Max.(V)Rep.Pk.Off Volt.=50
I(T) Max.(A) On-state Current=380m
@Temp. (�C) (Test Condition)=25
I(TSM) Max. (A)=800
I(GT) Max. (A)=1.0m
V(GT) Max.(V)=800m
I(H) Max.(A) Holding Current=4.0m
I(D) Max. (A) Leakage Current=100u
@Temp. (�C) (Test Condition)=100
V(T) Max. (V)=2.5
@I(T) (A) (Test Condition)=4.0
Status=Discontinued
Package=TO-92
Military=N

All I could find was a NTE 5402 which is suppose to work? I picked one up a bit ago at Electronic Supply Company.

http://www.nteinc.com/specs/5400to5499/pdf/nte5400_06.pdf

GENXVINTAGE
02-19-2009, 02:05 AM
Im founding out the further I get a long here that someone has screwed with these receiver and not in a good way. Im finding wrong components in spots, resistors where diodes should be and so forth.

Anyway my question is, "Does someone have a G-7000 that they could open up and look on the Power supply board F-2858 and to the left side I need to know or a picture of RO7, RO8, D09, and D10 area? I found the diodes in ther service manual but Im not having much luck on the resistors. Someone has put a resistor were the diodes should be along with a mylar cap and then ran a wire under the board over to one of the 10 ohm resistors for some reason? Dont know if they were trying to bypass the relay or what? But I need to know what ohm the R07 and R08 resistors should be?

EchoWars
02-19-2009, 04:38 AM
Post a schematic of the amp (just the amp, not the whole bloody receiver).

Hyperion
02-19-2009, 04:59 AM
If I might make an observation - you need to get away from the idea of replacing components pretty much for the sake of it. Try to take some voltage readings - from this information you can usually pin the problem down to a dozen or so components with 1 or 2 being hot favourites.

I know it can be really frustrating when you have a seemingly unfindable problem - stick with it, EW is so good at this.

Good luck

John

EchoWars
02-19-2009, 07:23 AM
No, I'm not. What I'm good at is fixing them myself. What I suck at is this web-based 'look here, do this, try that'. More often than not, whether it's my fault or the guy working on it, it all ends in grief.

Which is why you rarely see me orchestrating a step-by-step thread. I'll butt into other threads that Mark might be working on, but in general I'm too busy with my own stuff.

What doesn't help here is twofold: One, it's a Sansui, and their service manuals are notorious for errors...sometimes many of them for one manual. Two, I don't have the manual for this receiver, so we have the blind leading the blind. A recipe for disaster.

Hyperion
02-19-2009, 02:58 PM
Point taken - I am very poor at this as well - add that to my inexperience with anything that I do not own
another recipe for disaster :yes:

I realise now that your posts are more the 'surgical strike' variety - very good nonetheless.

John

I'll shut up now....

GENXVINTAGE
02-21-2009, 09:33 PM
Post a schematic of the amp (just the amp, not the whole bloody receiver).

I have the manual in a pdf and not sure how to extract just those two pages?

EchoWars
02-21-2009, 09:43 PM
Upload the whole thing to: http://www.yousendit.com/
...and post the download link here.

GENXVINTAGE
02-21-2009, 10:05 PM
http://www.flyupload.com/?fid=278299773

GENXVINTAGE
02-21-2009, 10:06 PM
http://www.flyupload.com/?fid=278299773

EchoWars
02-22-2009, 01:39 AM
Good Christ, that was painful. 9KB/Sec download. I thought I was back on my US Robotics modem. Dump those guys, they suk. Use USendIt.

Here's a scan of the corner of the power supply/protect board, F-2858. This is from the foil side. Measure the voltage at either side of R01 and R02. This is the output of the L & R amplifier channels, and we are wanting to see something close to zero volts.

http://img4.imageshack.us/img4/9056/powerprotfoil.jpg

GENXVINTAGE
02-24-2009, 12:23 AM
[QUOTE=EchoWars;2523546]Good Christ, that was painful. 9KB/Sec download. I thought I was back on my US Robotics modem. Dump those guys, they suk. Use USendIt.

Here's a scan of the corner of the power supply/protect board, F-2858. This is from the foil side. Measure the voltage at either side of R01 and R02. This is the output of the L & R amplifier channels, and we are wanting to see something close to zero volts.

Well Im getting R02 (-2.04V) and R01 2.52V?

On This board F-2858 I have had to replace TR02 / D13 / D14 / R613 / R610 /SCR601.

The red power light is now on and the green tuning and the tuner seems to be working now which wasnt before but still no output or second relay engaging.

Here is the photos of the red wire on bottom and the green cap that I think may be incorrect?

http://i288.photobucket.com/albums/ll176/genxvintage/Sansui%20G-7000/IMG_5743.jpg
http://i288.photobucket.com/albums/ll176/genxvintage/Sansui%20G-7000/IMG_5746.jpg
http://i288.photobucket.com/albums/ll176/genxvintage/Sansui%20G-7000/IMG_5749.jpg

Tichu
02-24-2009, 11:15 AM
Wow, someone has been here before !

The small diodes that are mounted on the bottom side of the board are not original, and a previous tinkerer has worked his way around and left traces of bad soldering for sure !
A case of "Frankenstein" board for MrMonster... :D

The green cap looks OK to me.

The voltage you measured (-2V and +2,5V) are very probably the reason for the relay not clicking.
They are just protecting your speakers from DC voltage.

You should try to adjust the DC offset on the driver boards, and see if you can set the voltage you read on these 2 resistors close to 0V (10 or 20 mV is OK).

GENXVINTAGE
02-25-2009, 11:36 PM
So is the manual wrong cause it shows resistors and diodes where that green cap is and no cap??

EchoWars
02-26-2009, 09:10 AM
The differences between what the manual shows and what you see are pretty common on Sansui gear.

Your measured offset, fairly equal from channel to channel, suggests a missing voltage supply somewhere. Check the regulated and unregulated voltage supplies at their sources.

GENXVINTAGE
03-08-2009, 12:36 PM
Ok Frustration is setting in!!
Does anyone have a G-7000 that can take me a few pictures of F-2858 Power Supply Board, top and bottom. Its hard for me to determine to much on how screwed up this thing is along with Sansui's crappy ass service manual!! Im spending more time trying to determine if the part in the receiver is correct (which a few have not been) or if the manual is wrong (which is for sure in a few spots)!