[sdiy] Oberheim OBXA issues

Peter Pearson electrocontinuo at gmail.com
Sun May 1 02:06:53 CEST 2022


Serious question, not being flippant - do you have the memory protect
engaged?  If I had one American dollar for every time I've gotten
sidetracked by something dumb like that myself...

On Sat, Apr 30, 2022 at 7:31 PM al spitzley via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Hello all,
> So I am working on a DOA OBxa. I've got it up and running after power
> supply rebuild and a lot of troubleshooting.
> Now I'm stumped with a couple of issues that could be related to each
> other.
>
> Firstly when I enable the cassette mode it doesn't seem to go into the
> mode. The Cassette LED does light, but the other LEDS do not go out. The
> Play button or seemingly any other button are non responsive.
>
> Secondly when I write a patch to load the patch I have to hold the
> relevant Program button. As soon as I release the button the patch
> disappears.
> Scoping the power rails shows a significant amount of noise. If I disable
> the clock the noise goes. I've tried replacing numerous ICs around the CPU,
> including rebuilding the clock but still there is a bunch of noise. I'm
> hoping this noise is causing the issues I've mentioned but am struggling to
> work out what is causing it. Or maybe that is not the problem?
>
> Any ideas greatly appreciated.
> Thank you!
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