[sdiy] Troubleshooting Roland PG300

[Travis Thatcher]

I'm working on a PG300 for a friend of mine. He said it was working
for a little while when he got it and then one day just stopped
sending data.  At first look all connections checked out and the 5v
regulator was working properly. I Tested the inputs to the CPU with a
scope and saw voltages changing with the sliders, however on the
output side of the cpu, pin 17 there was no change.  The crystal is
good, and power seemed fine.  I heated up the board a bit with a hot
air gun to check for intermittent connections and briefly got some
sysex activity but it then the board cooled and ceased transmitting
again.  I went over most of the solder joints around the cpu/eprom and
checked the traces with a meter. Everything seems okay and I'm a bit
stumped.  I'm planning on removing the hex inverter, IC2 to test it
tonight out of circuit and see if perhaps it was pulling down the
output from the CPU...beyond that or a broken cpu I can't really think
of anything else.  Anybody have any ideas?

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