Vintage Synth Repair

<< I've been in the process of refurbishing a polysix and have done due 
diligence with regard to the usual suspects (i.e. battery mod). The 
only problem that remains is pitch drift caused by what I assume to 
be a voltage leak in the LFO causing a subtle modulation  of the VCO. 
I have a working Polysix as well, and have had the luck of being able 
to A/B the KLM-367 boards between the two units. The problem follows 
the board under repair (I thought it might be the KLM-366 board). The 
unit is a "New Production" model. Any suggestions? >>

yes- I had the same thing in a monopoly a few years ago. took me a while to 
figure it out.... look for the oscillator chips themselves; they will have a 
thermistor device glued to the top of them. the glue is supposed to keep the 
devices in close contact but eventually goes off & cracks, leading to freq drift 
instead of temp compensation.

remove the devices & clean them thoroughly- get all the old glue off. then 
arrange for the thermistor (or whatever the damn thing really is) to sit hard 
against the top of the chip while some new glue sets- I tied it down with a 
length of fine wire wrapped right around the chip until the glue dried, then cut 
the wire away again.

the tiniest air-gap is enough to destabilize these things.

it's possible that a webtrawl will reveal a modern replacement or better cure 
for this- the only korg box I have now is a vc10 which doesn't have these 
issues.

duncan.