[sdiy] EFM VCO 4e is singing a fixed frequency

cs e modulemania at gmail.com
Fri Feb 29 01:29:38 CET 2008

I've got the EFM VCO 4e singing, but at a fixed frequency.
The problem is the frequency can't be adjusted - by knob or any CV inputs.

It hard syncs to ext VCO, FM-in works, PWM and all waveforms look OK.
What would be stopping this thing from letting its frequency be
adjusted?  I hope the CV inputs OpAmp isn't bad  - that would be my
luck though, because I didn't use a socket on that one :-(

Little side note - while looking at some voltages with the scope and
the DMM, I saw a little magic smoke coming from the "FREQ" pot (the
one with +/-15V and the wiper going to the pcb).

Any troubleshooting tips here?


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