Vintage Synth Repair

The last of the Oberheim Service dept. parts, including matrix are with John L, 
at 403-543-5127  






________________________________
From: Joigaloid <andre_sand@...>
To: vintagesynthrepair@yahoogroups.com
Sent: Sun, July 11, 2010 7:21:18 AM
Subject: [vintagesynthrepair] Restoring my Matrix-12

  
Hello!  I have an Oberheim Matrix-12 that I would like to restore.  It spent a 
lot of time in storage (which caused a few problems) but there are a couple of 
functional problems I'd like to fix before attacking the cosmetic problems. 


The first issue is that I've noticed some notes were being dropped while 
playing.  After checking a few things with the tuning page I noted the following 
observations:

VCO Tuning:  Voice #6 fails
PW Tuning:  Voice #6 fails
Res & VCF Tuning:  Voices #6 and #12 fail
VCA Tuning:  Voice #6 fails

After tuning, the Matrix turns off the two failed voices.  I can always turn on 
voice #12 manually and get sound from it.  If I manually turn on voice #6, I get 
no sound from it.  All other voices are fine.

My guess on the above is that I've lost the Curtis VCO chip for voice #6.  The 
failure of voice #12 is more subtle, but it seems likely
I've lost the CEM3372 which performs all the filtering options.  I am faced with 
the frightening prospect of trying to locate a replacement 

CEM3374 and likely a CEM3372 as well. 

I will swap out chips between voices, but would prefer to keep swaps to a 
minimum.  The Matrix-12 has two identical voice boards, I'll have to guess which 
one is voices 1 through 6 and which one is voices 7 through 12.  Any 
suggestions?

I will be posting my experiences on this project both on the vintagesynthrepair 
and on the oberheim yahoo groups. Hopefully, others may benefit from them, and 
of course, I am open to any tips or suggestions from the group.

-as