Vintage Synth Repair

Hi all,

Please keep in mind I'm new to troubleshooting and repairing vintage 
synths..

I recently acquired a CS-50.  It has 2 problems though: the touch-
sensitivity is not working and one of the voice cards tracks the 
keyboard, but with a pitch about 4 or 5 octaves above the other 
voices-- this voice squeeks instead of squaking.

Since I have 3 perfectly fine voice cards, I figure I can use one of 
those to pinpoint the problem in the faulty card.  I'm armed with a 
radioshack volt-meter, but I'm not sure where to go from here.  
Would the best method be to measure voltage between components and 
do a one to one comparison?  Say, if the voltage differs in the same 
point on both cards, I would know the problem is in that area and I 
could simply replace that component?  Does this sound like the right 
strategy? Unfortunately I don't have any schematics, and only a 
partial service manual for the cs-80 is on the web (nothing on the 
voice boards).  I'd appreciate any tips/suggestions.  Thanks.