[sdiy] Topic cem3396

[WeAreAs1 at aol.com]

In a message dated 4/16/04 4:58:52 AM, pHobax at gmx.de writes:

<< Hi. I own a elka ek-22 with 6 cem-3396-voices.

A real annoying bug occured, effecting all six voices:

The synth doesn't produce the right waveforms anymore. The saw has a much

less amplitude on all octaves except an the 1st and 2nd.

PW is not real ajustable anymore, it seems to depent on the note played. 

With some ajustments the PW is 0 on c3.

Tri isn't accesable anymore etc....

In addition the seperate voices vary in their volume (not very strong, but

it sux) and the described bugs.

This problem seems not to be located in the chips.

I thoght  the divider or the digital osc could be the reason. >>

Hello Max,

You're right that the problem is not with the CEM chips.  It's very likely 
that you have a bad multiplexer chip somewhere.  Look for any chips that are 
numbered "4051".  Assuming that you don't have a schematic for the synth, try 
replacing these 4051 chips one at a time.  If that doesn't fix it, you might have 
a bad buffer opamp after one of those 4051 chips.  If replacing thos parts 
doesn't fix it, then you might try taking a look at the DAC chip which 
distributes the CV's to the 4051's.  Good luck.

Michael Bacich