Matrix 6 questions

[Thomas Loop]

Hi.

I recently bought a battered Matrix 6 and I am quite impressed with the
sonic possibilities of the synth.
It has a few problems, though and I thought someone on this list could
perhaps help me with these.
Hope this is not off-topic because it is a maintenance question and has
nothing to do with building stuff...

The first problem the board has is that 2 voices are slightly buzzy. 
When I put the voice assignment in "rotate" mode I can clearly hear a buzzy
overtone on voice 2 and 4 (on voice 2 just slightly, on voice 4 a little
louder)
This gets a little annoying, especially if the filter is half closed.

Can anybody with a Matrix 6 service manual tell me if it is possible to
calibrate the voices/filters?
I opened the synth and saw 4 trimpots. 3 that look the same and one extra
with a different look.
I tried software calibration but it didn't help (I also know the trick with
hitting the store button on power-up for a full reset).

The second problem is that sometimes the synth just hangs itself. A new
power-up most of the times helps, sometimes I have to do a full reset to
get it up again.
In the AH archives I found some messages about quality problems with the
power supplies of these babies. 
Guess this could be the cause.

Any help would be greatly appreciated.

Greetings and thanks for your time.

		.loop.