Vintage Synth Repair

I've gotten another M500 on my desk now.


Main problem: three of the woodwind presets don't work (wood 2, 4 and 16),
everything else looks mostly ok.
Close inspection shows that at least one electrolytic cap has leaked on the
board. The cap in question is probably C50 (It's hard to read in the
schematic, and the acid has taken away part of the lettering on the board).
It's a 220uF/16V cap close to R133.
The acid has eaten through a couple of traces; for at least one trace
there's no continuity anymore. My guess at the moment is that this is also
the reason for the missing presets.


Now, the interesting thing is: This is the second M500 I'm working on that
has developed this particular preset problem; and if I recall the other one
had exactly the same leaky cap. I also recall that somebody else on this
list had an M500 with similar problems.


So I think it's likely that those leaking caps are the source of this. I'll
try to repair mine tomorrow and will report back then.
It would probably be a good idea to exchange this cap (and possibly the
other 220uF cap, too) in all M500 before it starts to leak. Why exactly
this cap leaks - I don't know. Maybe it's a manufacturing defect.