[sdiy] finding a short in a Yamaha CS-50/CS-80

[jpitt at fhcrc.org]

I recently bought a non working CS-50.  The previous owner said it was  
a blowing fuses and a power supply problem...I changed some leaky caps  
on the PSU and have tested the power supply and it's putting out the  
proper voltage, but I think there is a short to ground somewhere  
outside the PSU.  When I test the PSU voltage with the +15/+15S and  
-15/-15S supply lines shorted (as per the cs-80 service manual), I  
read the proper 15 and -15 volts on the PSU, but when I hook up the  
leads from the PSU to the synth, the +15 reads 1.5V and the -15 reads  
-0.6V.  I checked the resistance across the mounting rack rails for  
the voice boards, which should carry +15 volts and ground, and I'm  
only reading 220 ohms, which makes me suspect the 15 and -15 volt  
supply is shorting on one of the 11 circuit boards in the thing.  I  
visually inspected the boards and can't see anything obvious.

Do I have to desolder every single +15 and -15 line off every board to  
track down the short or is there an easier way? The amount of wiring  
in this beast really makes me appreciate modern synths :)

-jason