Vintage Synth Repair

I've got one of these that blew up in a wild show of sparks and smoke 
one day, suprisingly, looking inside I see little to no damage and It 
will sometimes work for a little while after powerup.  The external 
input works fine and if the rez. is set to max and key follow turned 
on it tracks in tune just fine.  When the oscillator sliders are 
turned up the sub octaves can be heard, but are sounding around 10-
16k, the regular oscs presumably are out of range.  I've checked the 
power supply and I get two 0v leads, 2 +15v and 2 -15v leads so I 
assume the problem is not there.  Does anybody have any information 
that could help?