Re: [AH] Yes you CAN get a Memorymoog to stay in tune

From Brian Willoughby
Sent Sat, Mar 10th 2018, 01:41

Thanks for the report, Michael. Should be great information for the =
archives.

Meanwhile, I had intended to respond to your earlier message about the =
=E2=80=9Cbad=E2=80=9D Z-80 with a hypothesis. I recently repaired a =
Roland CR-78 where one bit of a latch had partially burned out. The =
whole thing was working except for the Bass drum, and I tracked it down =
to that one bit. My thinking on the Z-80 is that it must have been =
mostly functional if it was able to run the synth apart from tuning, but =
perhaps there is a Port IO pin that is exclusive to tuning and which had =
gone bad. Not that you can repair an individual pin without replacing =
the whole chip, but I was curious. Typically, a CPU is either completely =
dead or totally functional. It=E2=80=99s actually quite rare to have =
some features fail while most are still working (at least not unless =
there is a bug in the firmware - in which case the same problem would =
appear on all units).

Again, thanks for detailing your work and discoveries.

Brian Willoughby


On Mar 9, 2018, at 5:32 PM, Michael E Caloroso =
<xxx.xxxxxxxxxxx@xxxxx.xxx> wrote:
> The last mile to the finish line was the toughest... autotune
> wouldn't.  Even though the display reads "6 TUNED" does NOT mean that
> it tuned the VCOs!  After isolating many of the support ICs and
> confirming the audio path between the VCOs and autotune circuit the
> root problem turned out to be.... the Z80.  EVEN THOUGH THE REST OF
> THE SYNTH FUNCTIONED.