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Sansui AU-9500 restoration issues

C

Carl J72

New Member
Have recapped a few amps and decided to try my hand at recapping my au-9500 using the wonderful illustrations and descriptions from leestereo's posting of scribby31's amp. Somehow I have made a mistake or two and am feeling a bit defeated, but I really loved this amp and figured it was worth a shot at asking for some advice. Basically 3 of the 4 decoupling caps have started bulging and 1 just about blew when I initially turned it on, also resistor 863 on both of the driver boards started smoking as well. The remainder of the boards appear to be ok.

Thank you in advance for any help.
 
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Carl J72 said:
Have recapped a few amps and decided to try my hand at recapping my au-9500 using the wonderful illustrations and descriptions from leestereo's posting of scribby31's amp. Somehow I have made a mistake or two and am feeling a bit defeated, but I really loved this amp and figured it was worth a shot at asking for some advice. Basically 3 of the 4 decoupling caps have started bulging and 1 just about blew when I initially turned it on, also resistor 863 on both of the driver boards started smoking as well. The remainder of the boards appear to be ok.

Thank you in advance for any help.
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Why aren't you using a DBT?

You obviously wired the caps wrong. Take them out, look at the schematic again. Keep the driver boards out until you have no glow on the DBT.
"Measure twice, cut once"
 
Sansui schematics are known to contain mistakes... I can't speak for the AU-9500, but others I've worked on have a few mistakes.

The work-around is to take photos prior to removing any components, and the big help for me... use a sharpie marker to mark the top of each cap oriented towards the front of the amp. This way, if I ever get confusion between the circuit board silkscreen, schematic, and the actual cap, I always put in the new cap the way the old one came out.
 
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I also mark old caps and take pictures before removing them. I use a red Ultra Fine Point Sharpie to mark the + side of each cap. In addition, and also make a hand drawing on blank printer paper that shows polarity and uF/voltage next to a circle representing each cap. That drawing is more convenient (than my computer monitor) to have near the amp when the new caps are going in.

DSC05311rs900.JPG
 
So I actually have another identical working unit to use as a comparison, wiring of the main filter caps matches the other unit and the schematic. The new caps are a larger capacitance (10000uf/63vdc), but same voltage, i wouldnt think brand new caps would cause an issue?
 
If you bought the new caps from a reputable source (like Mouser or Digi-key) then no, it is highly unlikely that they would cause an issue. If you got them off of ebay then all bets are off.
 
show the markings and install of the good amp and the markings and connections to the damaged amp to get more eyes on your particular issue. The 10000µF caps are what you mean by decoupling caps?
 
All the planning, reading and photos along with an identical unit to use as a reference should have been a good start. It proved not to be, similar to some of the recent responses, which one can always count on - 'end of story'.
 
Carl J72 said:
All the planning, reading and photos along with an identical unit to use as a reference should have been a good start. It proved not to be, similar to some of the recent responses, which one can always count on - 'end of story'.
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Lol.

I told you the problem, the caps are in backwards. If that’s not helpful, I don’t know what is.

Let’s start trying to fix the issue and move on, pictures and better descriptions would helpful, as you have given neither. Lots of members are trying to help - help us help you! Again as I said in my first post, why aren’t you using a DBT? Have you built one yet?
 
Carl J72 said:
3 of the 4 decoupling caps have started bulging and 1 just about blew when I initially turned it on, also resistor 863 on both of the driver boards started smoking
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This happened while on DBT? Where did you purchase the caps?
Smoked resistor usually = smoked transistor/s too, I'd check what mbz suggested.
You'll probably have a bigger job ahead of you now, just slow down and keep testing parts.
Don't take it off the DBT until (at least) the bulb dims correctly and the relay clicks. ID #s of dead parts you find will help others help you. As Ivan said, photos might help those experienced with the amp spot issues you may not see.
ivandezande said:
End of story. Don't care what the other unit looks like, you messed up.
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We've all messed up before, a little kindness can inspire a good repair!
 
You may want to post this in the "Exclusively Sansui" forum. You will receive help here, but your thread might get more attention in the Sansui forum.

Good luck to you, the 9500 is a wonderful amp.
 
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