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Sansui 9090 -Protection Mode

Check the output transistors they are probably shorted. Also there is a modification that needs to be done on the speaker relay board. Sansui thought it would be a good idea to short the speaker outputs to ground when the speaker relay is in the off position. There is no good reason to do this, and sometimes the relay contacts get welded together such that the power amp output gets shorted to ground, blowing the output transistors. Do the mod shown here:
http://www.audiokarma.org/forums/showthread.php?t=117552
 
Thanks for the advice on this - I'll make this mod as well as check the output transistors before putting the driver board back in.

dr*audio said:
Check the output transistors they are probably shorted. Also there is a modification that needs to be done on the speaker relay board. Sansui thought it would be a good idea to short the speaker outputs to ground when the speaker relay is in the off position. There is no good reason to do this, and sometimes the relay contacts get welded together such that the power amp output gets shorted to ground, blowing the output transistors. Do the mod shown here:
http://www.audiokarma.org/forums/showthread.php?t=117552
Click to expand...
 
I don't think the 9090 shorts to ground like the 9090db. Not positive, since its been a while since I've seen either one of these units.
 
tiga said:
So tonight I decided to replace the blown fuses and turn the unit on and see what happens. (I haven't had a chance to check the fusible resistors on the driver board yet). Well I power the unit on and I get smoke and then flames from the lower left corner of the driver board. Yikes! Two of the new fuses blew as well.

So is this an indication of another problem besides bad resistors on the driver board? Or is smoke/fire a possible result with bad fusible resistors?
Tiga
Click to expand...

If you find a blown fuse, there's a 99% chance it blew for a reason other than the fuse itself being at fault. If you find two blown fuses, there is statistically a 100% chance the fuses aren't the problem. I don't understand why anyone would replace multiple blown fuses and have even the remotest expectation that this will do anything other than burn up EVEN MORE components than had been fried before the fuse blew the first time. At minimum it will unnecessarily stress components a second time. At worst it'll cause a fire and blow up some more components. Live 'n learn.

If you want to troubleshoot equipment, build yourself a dim bulb tester. The cost of parts is about $10 (that's if you buy everything new, I was easily able to piece together one from parts I had on hand) and it'll save you many costly, time consuming and potentially frustrating repairs.

Just my 2 cents.
 
Bit of a zombie thread. Would anyone know how hard it'd be to make new pcbs from the art work? (Service manual?)
 
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