Yet Another Sansui 9090DB Rebuild Thread

[Penn42]

Trying to source a power switch this morning. Looks like there's currently one OEM switch available on the auction site right now as well as a generic replacement switch that's will supposedly work in many models including the 9090db. I think I'm going to go the generic route unless there's anything I should be aware of about that. The bummer is my twitch works fine, but the place arm the protrudes is broken behind the flange that captures the spring. Thus you have to pull the switch out manually. Also the original push on button is gone, which is a bummer because it's not just a little round silver cap, but the rectangular black cap. I haven't seen one of those pop up yet. I'll have to be diligent in my looking.

I'm also going through and starting to make parts list for some of the other boards I'll eventually get to. Are there any ceramic, mylar, or polystyrene caps in the unit that are known to be troublesome/commonly replaced?

Also, I have never replaced any components in a tuner circuit before. I do know that if you get to deep into one you'll need to get an alignment done. When I rebuild the tuner will there be any potential to damage the unit if I use it before getting an alignment or will the tuner just not work properly?

 

[LBPete]

Other than the power switch, don't start any mass replacement of parts before you get this thing working. There is no need to do anything with the tuner right now. If it comes out of protection with the driver board out, there is probably nothing major wrong with the power supply or outputs. Concentrate on fixing the driver board. Having a working unit gives you a base line. Without that baseline, if in the process of replacing parts you make a mistake, then you have compound problems to sort out and that can be a nightmare.

- Pete

 

[Penn42]

Everything has arrived and been installed except the STV-3H's from Germany. Is there any trick to getting the sleeving linked to in post 34 to keep from fraying so bad? I tried a flame, which didn't work. It looks exactly like all the old stuff that found in units, but it frays really fast. I used it to stand off all the resistors and it looks like crap.

 

[LBPete]

If it's the sleeve on the diode leads, it's not linked to anything. It just floats on the lead.

- Pete

 

[Penn42]

Parts came today. I installed the STV-3's, changed the 10A fuses on the power supply to 6A (something I read in an old thread is a prudent cautionary step) and put the unit on DBT. With f2624 in I've got a bright light. I've just finished spending 30 minutes with a magnifying glass and flashlight looking for solder bridges. I thought I got lucky when I found a cracked trace, but when I fixed it with a little 22 awg wire I've still got the bright light. I suppose another thorough sweep through the foil side is in order, I'll leave that for another day I think. What's the best procedure from here? Below are some amateur ideas from your humble OP.

Are any of the following possible culprits?

1. The rogue diode detailed in post #28. It's the only thing currently on the board that isn't mirrored on the other side. Is it worth replacing with a wire jumper to see?

2. I remember reading somewhere that depending which version of the board you have that the trimpot adjustments will be backwards. I can't find where I saw that. I've currently got all 4 VR's set at 12 turns. I don't think this is likely part of the issue, but perhaps it is.

3. My VD1212 replacements. I never actually got a confirmation test on the new pair I made out of two 1N4148's because my DMM doesn't supply a strong enough voltage. I know I built them correctly (anode to cathode) and I've got them in according to the illustration printed on the board. The board is correct if the tiny grey dots on the VD1212's is the cathode denotation. I've still got the originals I could put back in and also have a handful more 1N4148's if making another set needs to happen.