[sdiy] Memorymoog VCO trim

[Dave Magnuson]

----- Original Message ----- 
From: "dragon.servicing" <dragon.servicing at googlemail.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, June 16, 2008 6:47 PM
Subject: Re: [sdiy] Memorymoog VCO trim


> Hi,
> I think I read a while ago that the trimpots in the Memorymoog ( and some 
> other older synths ) can wear out causing unpredictable performance. I did 
> find this with a Minimoog I worked on a couple of years ago. ( but the 
> trim pots are probably a different type ).

<snip>

I had a very similar experience with my Crumar Spirit (a CEM-based synth 
designed primarily by Bob Moog).   The open frame trimmers in the VCO were 
exceptionally sensitive and needed to be replaced.

The VCO pitch used to jump around all over the place (randomly) due to a 
worn or dirty spot on the conductive strip.
Just barely touching the trimmers would cause a 5 or 6 octave jump.   If you 
cycled the power switch the synth would "settle" at a different frequency 
each time.    Swapping out the trimmers fixed it.

So I'm assuming this is a fairly common ailment on synths of this era.

Dave Magnuson