As your tech should know, after checking the power supplies,
you would check the oscillator to the CPU, and also the reset signal
to the CPU. If those are OK, then try reading the EPROM that holds
the code, to make sure it's still intact. (At some point you may also
want to upgrade to the one that's on my site, tauntek.com, but only
after you get it fixed) If everything is OK so far, then scope the
address and data lines coming from the processor and look for strange
voltage levels, which would indicate a signal that is shorted to vcc or gnd.
But test the synth first to see if maybe it's working and just the display
is bad. That would be a different situation.

The service manual for the Matrix 6 is available, so your tech should
get that if he doesn't have it. It's a free download. It least then he will
have the schematics.

Bob


--------------------------------------------

On Tue, 2/23/16, fknchino@... [oberheim] < oberheim@yahoogroups.com > wrote:

Subject: [oberheim] Re: Oberheim Matrix 6 Display Issues
To: oberheim@yahoogroups.com
Date: Tuesday, February 23, 2016, 1:59 AM


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Hey Bob, Thanks for the reply.

Haven't tested the audio outputs yet, the
audio out board assembly was fully disconnected at the time
I gave it to my tech, worth a try

I forgot to mention I also replaced the CPU.

Some of the CEM chips I
replaced had broken pins, hence the replacement.

Once the synth is fixed
I'll get back to you on the condition of the chips and
if you're interested in them.

Any possible scenarios you could come up
with

Appreciated

G