[sdiy] PG-300 woes pt 2

Travis Thatcher recompas at gmail.com
Tue Mar 12 15:35:45 CET 2013

It seems I've unfortunately hit a bit of a wall with this PG300.

Last night I checked the hex invertor chip out of circuit and it seems
fine. Also checked for continuity on all the traces for the cpu, eprom
and supporting components and everything checked out.  I'm wondering
if the eeprom got corrupted or perhaps the cpu itself is dead. I'm not
entirely sure how the multiplexor control works on these but I noticed
that no matter what control is moved, the address controls of the
mux's are all set to high, so taking the input from pin 4.  I'm unsure
if these control signals not changing is an indication of what the
problem could be. The output of each MUX does make it to the CPU.

There isn't anything weird that would require the PG300 to be
connected to a synth in order to properly function?  If I monitor the
output of the CPU, at pin 17 with a scope, I'm assuming I should see a
signal if it is properly working?  I was also checking, obviously,
with a midi monitor program.

Any help would be very appreciated, I'm kind of stuck!


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