[sdiy] Oberheim OBXA issues

chris chris at chrismusic.de
Sun May 1 23:31:29 CEST 2022


Are you sure the EPROM image matches the hardware revision?

I'm not familiar with the Xa, so I don't know if there have been
significant changes during its production run.

Chris



On Sun, 1 May 2022 16:10:00 +0000 (UTC) al spitzley via Synth-diy
<synth-diy at synth-diy.org> wrote:

> It did have a JL cooper kit installed when I got it. It was crashing with it installed so I took it out. 
> I put new epRoms in as it arrived with no EPROMs installed. I’m thinking maybe I need to try a new set. Possibly a new Z80 too,
> 
> Sent from Yahoo Mail for iPhone
> 
> 
> On Sunday, May 1, 2022, 2:47 AM, ulfur hansson <ulfurh at gmail.com> wrote:
> 
> do you have the original processor or midi kit installed? i know mine has been much more unstable since i added midi - no clue as to why though. squirrely notes, unreliable patch memory etc...
> sent from outer space
> 
> On 1 May 2022, at 00:22, al spitzley via Synth-diy <synth-diy at synth-diy.org> wrote:
> 
> 
> 
> Worth checking, but no, the memory protect is not engaged. But it is definitely the kind of thing that’s tripped me before!
> 
> 
> Sent from Yahoo Mail for iPhone
> 
> 
> On Saturday, April 30, 2022, 5:07 PM, Peter Pearson <electrocontinuo at gmail.com> wrote:
> 
> 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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