[sdiy] Oberheim Matrix 6 intermittent problem

[harrybissell]

There are some buttons you hold down during power-on that will
put the thing into a reset mode. I forget which, sorry.

Also, the memory reset circuit sucks.  The memory chips run on 4.3V
which gives them crappy margin to start with.  I changed the diodes
in the memory power to shottky (1N5817) to get higher voltage (at the
expense of battery life at really, really high temperatures :^P

eventually I re-soldered all the connection on the CPU board as well...
so the 're-seat' everything might be good advice. But beware you are
looking at a VERY common bug !!!

If you found a flashlight battery for memory hold... that might BE
my old Matrix 6 you have :^P

H^) harry

"S. P. W." wrote:

> Hello,
>
> I recently bought a Matrix 6 (with keys)  and (surprise) it has an
> issue or two. I absolutely love it so am going to fix it come hell or
> high water.
>
> When playing ocasionally all sound output will stop. When that happens
> I think the menu stops responding to the keypad. A power cycle will
> always fix it right up. This happens maybe once or twice a week, not
> every day or every time I play it.
>
> Not a big deal in my basement, but could be a problem at practice or
> especially on stage.
>
> I have done the master menu > calibrate function. I am assuming the
> calibrate on power up does the same thing. Should I try calibrating at
> every power up?
>
> I am good with electronics, and read today that reseating all chips is
> a good idea, so will do that very carefully due to static damage being
> possible.
>
> At first blush, this problem looks like some sort of voltage collapse
> that "shitshot's" the CPU clock. My first guess is to replace all
> capacitors with new high quality items, as caps have a finite lifespan
> that is very near to the age of this synth. (15 years is a rule of
> thumb. These are close to 20)
>
> If someone knows a better place to look, or has run into this before
> and knows the answer, I would love to hear it.
>
> take care,
>
> Steve
>
> P.S. Hi all, I just finished rebuilding my Moog opus 3 from a pile of
> parts, and bypassed the missing chorus with a jumper by going around
> the squelch circuit. I have the skills to fix the M6, but a pointer in
> the right direction would be a great help.