View Full Version : 9090DB Fusible resistor replacement with regular fuses?


Jonathan75
03-07-2009, 06:03 PM
Does anyone have a late production version of the 9090DB with fuses in place of the fusible resistors on the Power Supply Board? Pete gave me a heads up on that but I just need to find out what value fuse to use. I have some 5A Fast Acting fuses laying around with legs on it but not sure if that is too low or high?

With HomerJSimpson's help I found that R30 and R31 which are 1.0 ohm 1/2W Fusible Resistors that comes after the yellow transformer wires were totally open. I am hoping that after I replace them it just might start working. :music:

Radio Shack does not sell the resistors so I want to try the fuse route so I don't stall progress while I have time on the weekend.

Robisme
03-07-2009, 06:27 PM
Could be 1.5 amp 250 volt.

I modded my 8080Db. Check this (http://www.audiokarma.org/forums/showthread.php?t=165956&highlight=8080DB&page=2) tread.

Rob

naderpe
03-07-2009, 06:40 PM
I think these will work fine... two 1.5 amp and one 1 amp fuse. These are smaller than factory installed however should work. Make sure they are inside a plastic tube as original late production.
PM me and I will send you the three fusses if you don't have the amp value.
Peter

bobforapples
03-07-2009, 07:35 PM
I think these will work fine... two 1.5 amp and one 1 amp fuse. These are smaller than factory installed however should work. Make sure they are inside a plastic tube as original late production.
PM me and I will send you the three fusses if you don't have the amp value.
Peter

I searched and searched for those fuses, what are the digi-key part numbers? I'm gonna order 20 of em, thanks!

Jonathan75
03-07-2009, 08:29 PM
Thank you for everyone's feedback. Pete I appreciate your offer to send me some fuses. I will try first to copy after Rob and mod it with a Chassis-Type 4-Position Fuse Block. But I am curious why it is recommended to use fuses inside a plastic tube?

This is what I am thinking about.

http://www.radioshack.com/product/index.jsp?productId=2062258

and

http://www.radioshack.com/product/index.jsp?productId=2103764

Robisme
03-07-2009, 08:34 PM
Should be fine.

The plastic tube was probably so the fuses would not short to anything while they were hanging about.

A quick cheap mod Sansui made.

I have no troubles with my mod.

Rob

Jonathan75
03-07-2009, 08:40 PM
Now the agony of waiting for Radio Shack to open at noon on Sunday. Good thing the clocks spring forward tonight, one less hour to wait to see if my 9090 will come to life! :banana:

LBPete
03-07-2009, 08:52 PM
Looks like you got your answer regarding the fuse value. You can hack off two of those fuse holders to make that block a little smaller. You can probably mount it somewhere under the power supply so it doesn't look tacky with the top cover off.

- Pete

Robisme
03-07-2009, 09:21 PM
You can probably mount it somewhere under the power supply so it doesn't look tacky with the top cover off.
- Pete

Hey!

http://i97.photobucket.com/albums/l204/rob9167/100_3158.jpg

Rob

Jonathan75
03-07-2009, 10:14 PM
Well one step forward but two steps back. I rigged up some fuse holders by modifying some red wire caps with some 1/2 amp fuses and wire I had laying around. Now I get power to the tuner and I can see it tune a station! But..... now it won't come out of protect and the light flashes red. If I remove the fuses it will come out of protect and go green. I am open to any suggestions on what to check next.

Jonathan75
03-07-2009, 10:38 PM
For diagnostic purposes would it do any harm to remove the vertical standing board (F-2624 Driver Circuit Board) from the Power Supply Circuit Board? I wanted to see if with it removed it would come out of protection to possibly isolate the problem.

HomerJSimpson
03-07-2009, 10:52 PM
For diagnostic purposes would it do any harm to remove the vertical standing board (F-2624 Driver Circuit Board) from the Power Supply Circuit Board? I wanted to see if with it removed it would come out of protection to possibly isolate the problem.

no prob at all. In fact this will tell us if the problem is the driver board or the outputs. I suspect the fuseable resistors that are on the driver board...

LBPete
03-08-2009, 12:33 AM
Check the outputs! There is a reason those fuseable resistors were fried. Also, you need to check the fuseable resistors on that driver board.

- Pete

Jonathan75
03-08-2009, 10:16 AM
Thanks Pete and Homer. I powered up the unit with the Driver Board removed and it came out of protection. So I checked every fusible resistor on the board and found some bad ones. Do I just replace them with new fusible resistors or is there another upgrade for this board also? Here are the results. Now I will check the transistors.

Bad R34 = 269 k ohms
Bad R33 = Open
OK R35 = 5.5 ohms
OK R36 = 5.2 ohms
OK R39 = 10.4 ohms
OK R40 = 10.2 ohms
Bad R41 = Open
Bad R42 = 39.4 k ohms
Bad R43 = 44.7 k ohms
Bad R44 = .978 k ohms
OK R47 = 5.3 ohms
OK R48 = 5.3 ohms
OK R49 = 5.2 ohms
OK R50 = 5.2 ohms

http://www.soaporganicnc.com/9090DB%20Driver%20Board%20Conductor%20Side.jpg

http://www.soaporganicnc.com/9090DB%20Driver%20Board.jpg

hpsenicka
03-08-2009, 11:07 AM
There are at least a couple of threads already describing x0x0db driver board refurbishing in some detail.

In short, the best option is to replace all of the fusible resistors with metal film resistors, and recap the driver board while you have it under the iron. For bonus points, you can upgrade the trim pots while you are at it.

LBPete
03-08-2009, 11:45 AM
As has been said, there is a ton of information on refurbishing those boards. Do a search. Metal film resistors are the way to go. The 180 ohm and 150 ohm fuse resistors are the usual suspects but it doesn't hurt to replace all of them.

- Pete

Jonathan75
03-08-2009, 11:14 PM
Just regular metal film resistors or still get the fusible type that is also metal film?

nosirrah
03-08-2009, 11:49 PM
Just regular metal film resistors or still get the fusible type that is also metal film?

Just get the regular resistor, fusibles go out of tolerance over time, and don't provide any real protection anyway.
Casey

Jonathan75
03-09-2009, 12:03 AM
Thanks Casey

Jonathan75
03-09-2009, 09:32 AM
Does anyone know what the small brown diode is mounted to TR13 and TR14? I think mine is bad and it shows open but I can't find the part online. It only has two leads on it and says TR09 and TR10 on the board.

Also I hope I ordered the right trim pots. There was so many to pick from.

http://parts.digikey.com/1/parts/739141-pot-100-ohm-3-8-sq-cerm-sl-mt-3296p-1-101lf.html
and
http://parts.digikey.com/1/parts/739171-pot-5-0k-ohm-3-8-sq-cerm-sl-mt-3296p-1-502lf.html

CDFixer
03-09-2009, 12:29 PM
Just a note on the Fuses on some of the X0X0DB receivers in place of the fuse resistors. Those are only on the single voltage UL models that were sold in the US, Probably had something to do with getting the UL rating. I have never seen them on a multi-voltage unit, although there may be some that have had the mod done when the resistors opened.

HomerJSimpson
03-09-2009, 11:15 PM
If you need help when the parts come in, bring it by....

Jonathan75
03-10-2009, 05:47 AM
Thanks for the offer Homer. Hopefully I will have the parts by the time I get back in town.

Jonathan75
03-12-2009, 03:42 PM
It is working! Two fuses, eight caps and six resistors later it came back to life! Now I am trying to adjust the voltage and bias current. I wanted to get some baseline references before I changed the pots and wanted to see how close I am now. On my left channel it floats around from 17mv - 19.1mv and the right channel is 6mv - 10.5mv. But my bias current is 0mA. I didn't want to play with the pots because they are so old but I did measure them and they are both around 16 ohms. I didn't want to blow anything by tweaking on it until I replaced it but at 16 ohms out of a 100 ohm pot I should be getting some bias current right? I removed the fuse on left channel F04 and connected the leads between both points and I do not get any current at all. But I do get sound and everything seems to work fine. One thing I did notice is if you turn up the volume while you are testing with one fuse removed the sound will be distorted. Just found that curious. But anyway does anyone know why I would get no current?

Thanks

sui-san
03-12-2009, 03:58 PM
Check the fuse in your multimeter first.

sui-san

Jonathan75
03-12-2009, 11:03 PM
Thank you sui-san. I never thought about the fuse because I never used the amp meter function in this meter before. Guess the fuse broke from the years of travel with me. So I replaced it with a ceramic fuse in the hopes that it can take plane vibrations and baggage handlers better.

After the fuse replacement I was able to dial in the current setting. But I noticed that even after the four minute warm up period there is still some drift. It actually appears to drift down and not up during the current adjustment. Is this normal? And should both settings be rock solid? Because I get drift up and down on the current and voltage settings.

Anyway I am happy that it is singing for the first time for me! :music::yes::music:

nosirrah
03-12-2009, 11:33 PM
Thank you sui-san. I never thought about the fuse because I never used the amp meter function in this meter before. Guess the fuse broke from the years of travel with me. So I replaced it with a ceramic fuse in the hopes that it can take plane vibrations and baggage handlers better.

After the fuse replacement I was able to dial in the current setting. But I noticed that even after the four minute warm up period there is still some drift. It actually appears to drift down and not up during the current adjustment. Is this normal? And should both settings be rock solid? Because I get drift up and down on the current and voltage settings.

Anyway I am happy that it is singing for the first time for me! :music::yes::music:

That is normal, as long as you are in the specified range after a 20 minute warmup you are good to go.
Casey:thmbsp:

Jonathan75
03-13-2009, 07:03 AM
Thanks again Casey, that is a big relief. Now I just need install a permanent fuse holder and clean the unit up and it will be complete!

CDFixer
03-13-2009, 11:21 AM
The bias is dependent on the temperature of the unit (note the transistor or diode connected to one of the driver transistors) as the temp goes up the bias goes down to cool the unit, after cooling the bias may go back up, These drifts are normal. If you set the unit to measure the bias when you first turn it on when it is stone cold (overnight), it will probably be in the 70 to 80 MA region, then go down as things heat up.

Jonathan75
03-13-2009, 02:06 PM
Jim, thank you for the detailed explanation. I was wondering what that was and why when I tested it with the unit powered off it showed as an open. My concern led me to try and order the device connected to where TR09 and TR10 contacts are but I could not find a source to purchase it or a method of testing that mysterious square with two leads mounted to the heatsink of TR13 and TR14.

So should I set the voltage and current at the 4 min or 20 min operation mark? And should I play music at normal volume for that time period to make it more of a real world situation and temperature?

Thanks

nosirrah
03-13-2009, 10:49 PM
Jim, thank you for the detailed explanation. I was wondering what that was and why when I tested it with the unit powered off it showed as an open. My concern led me to try and order the device connected to where TR09 and TR10 contacts are but I could not find a source to purchase it or a method of testing that mysterious square with two leads mounted to the heatsink of TR13 and TR14.

So should I set the voltage and current at the 4 min or 20 min operation mark? And should I play music at normal volume for that time period to make it more of a real world situation and temperature?

Thanks

At the 20 minute mark, and do what ever you wish as long as it's all set to minimum when you adjust, it will be a little warmer in operation, because the case will be back on.
Casey

Jonathan75
03-14-2009, 08:03 AM
Thanks Casey, I will double check it today.

Jonathan75
03-14-2009, 02:00 PM
Here are the pictures of how I did the fuse upgrade. I know it is a bit obvious and not very pretty but I wanted to make it easy to check and replace the fuses.

http://www.soaporganicnc.com/Fuses%202.jpg

http://www.soaporganicnc.com/Fuses%201.jpg

http://www.soaporganicnc.com/Fuses%203.jpg
Put on some split loom to protect the contacts and wire some.

http://www.soaporganicnc.com/Driver%20Board%20F2624.jpg
Changed out the caps, pots and resistors on the Driver Board.

http://www.soaporganicnc.com/Meter.jpg
Couldn't leave this out. It sounds so good! :music: Thanks for everyone's help and advice! :yes:

naderpe
03-14-2009, 11:39 PM
Nice work

nosirrah
03-14-2009, 11:44 PM
Looks good to me!
Glad to hear all is well in Sansui land!
C

Jonathan75
03-14-2009, 11:57 PM
All is left is to clean up the outside. I will post some before and after pictures when it is complete. This unit was very dirty on the inside and the outside. :sigh: