[sdiy] PG-300 woes pt 2

Richie Burnett rburnett at richieburnett.co.uk
Tue Mar 12 16:18:57 CET 2013

There should be plenty of activity on the i/o lines from the micro as it reads the multiplexed pot levels and switch positions many times every second. If you're not seeing a hive of activity then I would suspect a faulty CPU clock, CPU being held in reset, or corrupt program memory.

You said that it momentarily worked when you heated the board. This is unlikely to help a corrupted ROM, but high temperatures are known to aid the starting of oscillations in crystal oscillators that are marginal. Also check for any damp or flux residue around the crystal and it's connection to the CPU.

Check the reset pin status to check it's not being held in reset all the time!

If any chips are in sockets, i'd suspect poor contacts, and remove and re-insert them just in case.

Good luck. And let us know the fault when you get it working!


Sent from my Sony Ericsson Xperia ray

Travis Thatcher <recompas at gmail.com> wrote:

>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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>Synth-diy at dropmix.xs4all.nl

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