[sdiy] Bizarre Xpander Tuning Problem

Michael E Caloroso mec.forumreader at gmail.com
Thu Aug 12 03:22:22 CEST 2021

Troubleshooting autotune malfunctions separates the men from the boys.
Lots of potential failure points, and it's a complex control loop.

One trick is to short the contacts of the autotune button; this puts
autotune in an infinite loop for probing with a 'scope.  If you
disable all but the problem voice, you can view the autotune action of
only that voice.  Triggering might be a challenge.

I once had a Memorymoog autotune malfunction that turned out be the
CPU.  Even though the rest of the synth worked, autotune did not.
There was a faulty register on the defective CPU, which was only used
by autotune.  That was after checking the signal path, the counter,
the DEMUX, swapping RAM chips around...

...you can't rule out ANYTHING - even the least likely culprit like a CPU!


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