Vintage Synth Repair

Thanks for all the answers.

Yes, checking the psu and power rails makes a lot of sense. Perhaps 
there�s nothing wrong with the cpu chip, but I can�t trace what�s going 
on.

I do own an MC-202 and while the sound gen section is similar to the 
101, the cpu part isn�t. But the manual is much clearer and helps a bit 
to understand how the psu works...

So, just soldered new decoupling caps to the cpu and fixed a few 
possible dry joints and the unit makes sound now (everything from the 
oscs, filter and env works ok, except for the s&h and vco range).

Still the problem remains, this time the hold led is continuously lit 
and the key transpose led lights on and off at a slow, fixed rate. The 
sound is on hold mode autriggering on and off at the same rate. And 
doesn�t respond to keyboard also. 

I�m testing the unit open. Perhaps closing it, with all the ground 
wires from cv/gate connected to the chassis will make it work? Sorry 
for such a dumb question...