Vintage Synth Repair

--- In vintagesynthrepair@yahoogroups.com, Terje Winther <terjewi@...>
wrote:

> The most likely candidates are:
> - Loose contacts somewhere
> - some transistor or lowcost opamp that acts as a amplifier need to be  
> changed
> - some capacitor has losts its value (or shorted out)
> 
> Can you still get VCF feedback with resonance at full?
> I had an ARP in once that was "dead", but I could get the filter to  
> oscillate, and hence the fault was in the signal chain before the  
> filter.
> You need the service manual to start checking (following) the signals.
> 
> tw.
>

I'm wondering if the envelope generators are firing.

Try manually changing the VCF cutoff frequency and see if that changes
the sound heard when the VCA gain is up.  If so, the filter is working
and it may be that the EG's aren't being triggered, which takes you to
the EG's and to whether or not it's simply no gate or no trigger from
the keyboard buss.

ARP filters are sealed units and are not subject to easy component
replacement.

And, when I suggested listening to the Test Points in the manual, I
actually meant listening to them.  Shunt the output of the audio test
points (not the CV signal ones) to the output of the Odyssey and see
where the signal drops away.