VCO CEM problems.

[Paul Schreiber]

Greetings from the CEM Master!

Are you saying that if you connect the LFO board and the VCO board to the supply, it causes the VCOs to drift? 
If you removed the LFO board, the drift stops?

Paul Schreiber
Synthesis Technology


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From: 	BJ[SMTP:zzynt at algonet.se]
Sent: 	Wednesday, May 14, 1997 12:51 AM
To: 	synth-diy at horus.sara.nl
Subject: 	VCO CEM problems.

There have been discussions about power supplys here a time 
back.

Are there any one that have had problems with a LFO switching
that are make interference to a VCO module.
The VCO are a CEM 3340, or more likely there are 3 of them on
the same PCB.
My design are very carefully laid out on the PCB.
The VCO are changing in frequency wery wery slightely!

The LFO have separate Regulators7805/7905 and 220µF filter
capps.The 2 PCB's are runing from the same supply.
The supply can deliver +/-2A.
The VCO PCB have no regulators but 440µF on both rails.

The LFO design are a basic Integrator type.
LFO design are made with CMOS.

Is this solwed with a separate supply for the VCO PCB,
does any builder on this list run their modular system with
separate supplys for different modules to gain for highest performance.

I have tried to decoupling the boards with separate 1000µF capps, but
the supply don't stay stable?????

The Lab supply are all OK, i have made a check on it!

Perhapps the CEM master have some clue?
Asks BJ in sweden.