Discussion about the Korg PolySix synthesizer

Hi everyone!

Just got into the exciting world of PolySix yesterday, when I was
given two p6's for free!

One is in great shape, though suffered some battery damage. the other
is a near write-off with sever corrosion on several areas of the main
boards.

After repairing all bad traces and vias (AFAIK) on the good p6, and
replacing the IC31 SN74LS08 with a SN7408 (note the lack of LS),
things seem to only half-work.

The sub-osc doesn't appear to work, the ADSR only sort of works
sometimes, the effects don't work, but there is a slow delay that is
constantly applied to the signal.

The programmer does not function at all. Sometimes program lights 2
and 5 will be on, other times just 3. Pressing any of the buttons on
the programmer has no effect.

I'm wondering if I really should replace the IC31 7408 with a 74LS08.
The difference being that the LS has zener diodes, and different
(higher?) impedance.

Any suggestions on where to look next?

Also, I believe the delay chips will need to be recallibrated. Are the
trimmers on the bottom of each BBD section the bias or offset
controls? OR neither?

Thanks in advance!

Sean