[sdiy] Prophet 10 on fritz again.

[Barry Klein]

Freeze spray & heat gun time....

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Steve Galle
Sent: Thursday, May 12, 2011 4:26 PM
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] Prophet 10 on fritz again.

This instrument continues to exhibit lots of character...

This time various parameters of patches (it's hard to say which, maybe all)
are drifting as it warms up, until patches no longer resemble anything
similar to what they're supposed to sound like. It's affecting all voices of
both voice cards, so it seems like it's got to be something on the CPU or
power supply I'd think. The polymod circuitry is independent for the upper
and lower voice cards so for now I'm ruling that out. The cpu also remains
stable so I'm thinking it's probably not an issue with the +5V. So I think
maybe I'm down to the +/-15V power supply rails, and components related to
the DAC system. I have a spare DAC71, so I will swap that out tonight and
see if that's it. I'll also test the power supply cool and warm. If the
supply is clean and the problem persists with the spare DAC then I'm not
really sure. There's the lf356 on the output of the DAC; it'd be easy enough
to swap in a replacement for that. Also the recent thread regarding
capacitors makes me think, m  aybe the next step is to recap the cpu board.
Tedious task to contemplate, but one that I suppose should probably be done
regardless...

Any thoughts appreciated; going to test the PSU and swap the DAC tonight,
fingers crossed. 

Steve
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