Vintage Synth Repair

A bad cpu is rarely the issue.  In the tr-909 the blame is often the cpu but the real cause is usually the caps/traces/switching transistors on the reset circuit, located back on the power board.

Some cpus have a circuit that protects them from switching on until they have a stable +5 v from the power supply, to prevent memory scrambles of what your saving.

You might want to check to see if the matrix cpu has a reset pin and trace that trace back to the power supply.  A transistor may be slow to fail, or a ground cap is a bit flaky and as they heat up something lifts internally or external to the component.  On the 909 traces are delicate and its easy to melt one that is hidden by the big capacitors  that it cuts across underneath, continuity trace catches if that is teh issue.  So teh circuit does what its supposed to when part of it fails

when the reset drops below 5V and it immediately switches the cpu off, which leaves the display hanging or blank  in mid-operation?

Just musing aloud not speaking from any matrix experience.



Lorne in Canada

rom: vintagesynthrepair@yahoogroups.com [mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of tim p
Sent: January-30-14 1:59 PM
To: vintagesynthrepair@yahoogroups.com
Subject: RE: [vintagesynthrepair] Re: Matrix 1000 Freeze.





Please define what you mean by "cpu has been changed"...

  _____

From: plat@...
Sent: ‎30/‎01/‎2014 21:42
To: vintagesynthrepair@yahoogroups.com
Subject: [vintagesynthrepair] Re: Matrix 1000 Freeze.



Hi everyone.

I have a Matrix 1000 that I am trying to bring back to life.

The issue is as follows:

I can turn it on just fine but it will freeze after a few minutes , this happens even though I just leave it alone.
Sometimes it will also randomly change presets but that does not happen often.

I have reseated all socketed chips,checked that battery, done the initialization but it keeps freezing.
CPU has been changed (I have two more CPU´s) * Software is 1.11

Any thoughts ?

Thanks
Arnar