Restore + Repair Yamaha C-2a & C-80 / M-80

It's got something shorted or failed... I was trying to poke around using a dim bulb tester but keep getting smoke even with the limiter... it seems to have gotten worse... for awhile it wasn't smoking at all?
 
value are good see my picture coming from original color service manual

View attachment 1276626
Thanks clinic-audio... I have the right values in there now but I don't think that's my issue currently. That might have been the original issue. But I have done something, or something has changed, and now it's messed up to the point of not knowing how to get it back on safely...
 
Easy to get back safely
Replace all burned components
Take of all the 4 transistors you touch
Check what voltage you have on both channel at collector TR521 ,522 (2SA912Q) = +0,8V and collector TR525 ,526 (2SC1885Q) = -0,6V
 
Easy to get back safely
Replace all burned components
Take of all the 4 transistors you touch
Check what voltage you have on both channel at collector TR521 ,522 (2SA912Q) = +0,8V and collector TR525 ,526 (2SC1885Q) = -0,6V
Great, I will start working on this!
 
in the meantime, not that this will probably have any positive effect but i took some pictures to see if you guys can see a mistake i cant...
 

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Easy to get back safely
Replace all burned components
Take of all the 4 transistors you touch
Check what voltage you have on both channel at collector TR521 ,522 (2SA912Q) = +0,8V and collector TR525 ,526 (2SC1885Q) = -0,6V

I took your instructions:

With the black/negative lead on the chassis... and the red/positive on the center pin (the collector) of each transistor I got the following results:

TR521 = + 36.47V
TR522 = + 38.6V

TR525 = + 35V
TR526 = + 37.85V

No more smoke with the four transistors out... I assume you meant for me to take them out. they were left out to take the measurements.
 
I took your instructions:

With the black/negative lead on the chassis... and the red/positive on the center pin (the collector) of each transistor I got the following results:

TR521 = + 36.47V
TR522 = + 38.6V

TR525 = + 35V
TR526 = + 37.85V

No more smoke with the four transistors out... I assume you meant for me to take them out. they were left out to take the measurements.
Now measure the base pads for voltage.
 
and about the base ?
the voltages aren't stable...

I'm redoing them to get the base and emitter and double checked the collector again...it's fluctuating all over the place... I'm getting the right voltage for 1 or 2 seconds and then its spiking back up to around ~30-40V where it stays somewhat stable... it's the same on the base and collector...the voltages aren't stable...
 
I think it might have something to do with where I'm connecting ground... I was just clipping it on to the chassis but I think that might be influencing the measurements
 
Well, I tried experimenting with a different ground location and used a different meter... I got similar results... I'm not sure about the fluctuation but these appear to be the most stable numbers:

TR521
C = +36.5v
B = +36.04v
E = +36.6v

TR522
C = +38.7v
B = +38.7v
E = +37.9v

TR525
C = +35v
B = -36.8v
E = -37.3v

TR526
C = +37.9v
B = -40.5v
E = -40v
 
Do you still have the transistors removed? you should have near zero volts on the collectors, With the transistors removed.
 
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What values have you got installed for R529,530,531 and 532?
 
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