Matrix 12 & CEM3372, CEM3374

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Matrix 12 & CEM3372, CEM3374

Post by Z » Tue Nov 10, 2009 4:31 am

OK, so I got that M-12 that was on the Austin CL (but was in Dallas metro area). It belonged to seller's late father and was told by his tech that only 6 voices worked. She did not have an amp to text it, but it did power on. I ran the tuning proceedure and everything failed: VCO, PW, VCF, RES & VCA. I took it home taking a chance that it might work.

First, I got no sound from both keyboard and MIDI. Later, I discovered that the M-12 disables any voices that do not pass tunig proceedure. I manually turned on all the voices. Voices 1-6 sounded (WAY out of tune) and 7-12 are silent.

Does anyone know if there may be anything wrong besides the CEM chips? I certainly hope so because I cannot locate the CEM3374's anywhere. There's a couple of matched sets of CEM3372's on eBay. And if it is the CEM's that need replacing, does anyone know where I can find CEM3374's (neither SynthTech nor Vintage Planet has them)?

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Re: Matrix 12 & CEM3372, CEM3374

Post by rjd2 » Tue Nov 10, 2009 4:20 pm

dont assume anything. i've seen opamps that are just south of VCO chips go south. w/ no scope, never would have found it.

my suggestion:

1: MAKE ABSOLUTELY SURE you discharge any static in your hands. wristguard good, not critical IMO.

2: swap CEM chips from working to non-working voices. this will at least identify if its that chip or not.

another thing: on my M12, i've noticed that the machine needs to have EVERY internal harness sat snugly and properly. one thing i would also do is go thru every harness, unseat, blow out w/ compressed air, reseat SNUGLY. but if you have 6 working, 6 non-, the harnesses are unlikely as a culprit for this particular problem.

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Re: Matrix 12 & CEM3372, CEM3374

Post by schmidtc » Tue Nov 10, 2009 7:23 pm

I'm guessing there could be quite a few things up beside bad CEM chips, so yea, try swapping them. Hard to say, until you open it up and start poking about.

CEM3374's are usually pricey (>$100) and hard to find. The best source for them is probably a busted chroma polaris.

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Re: Matrix 12 & CEM3372, CEM3374

Post by sam » Wed Nov 11, 2009 9:17 am

This feels like the DAC has failed.....:(

Hey schm...Thanks for the sonic help.. :D
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