Vintage Synth Repair

I just bought a sonic six, and when I fired it up, there was a brief moment when all was well and the unit was working,�but then it became unresponsive. Upon opening the case, I found the -15v regulated�pin had loosened and shorted to the +15v unregulated pin. Bummer. I replaced the components in the -15v circuit, (which had been done before, some traces were in poor shape), and fired it up again, but no sound at any output point... AND, after holding -15v for about a minute, it shoots to about -21v.�The regulator IC, (a 723 if I am not mistaken), gets hot to the touch... I have been looking the schematics over, but any ideas would be greatly appreciated...

I'm just a hobbyist, but if it were me, I would socket and replace IC10 
and IC11 (both 723's) as well as all electrolytics (C4, C5, C7, etc.), 
diodes and the 2N3055 power transistors in the power supply. They've had 
a hard life. All those parts together will cost less than $20. Then 
before I even thought about hooking up the rebuilt power supply, I would 
look for and replace any shorted components on the system boards. 
There's likely one.

Regards,
Mike