[sdiy] Memorymoog VCO trim

[James R. Coplin]

I replaced *every* connector with gold plated.  There is so much chained
together in the MM that it doesn't take much to dirty up signals downstream.
Some folks at the time told me this was unnecessary and I won't say they are
wrong, but my stability improved markedly after I did this.  Once the
sockets and caps had been replaced, it really became rock solid.  I used
some Bourns multiturn trimmers in mine, I don't remember the model number
off the top of my head.  A tech I know told me that a good trick if you
don't want to buy new trimmers is just to rotate the trimmers around on the
board so that you will be using a different part of the carbon in the
trimmer.  It's a cheap fix when you've worn through a spot.  

The odd thing I noticed is that my MM had several different types of
trimmers (brands and makes that is) and all of them looked to be original.
A friend of mine who is the original owner of his MM said his was the same
way.  Both of them are from the last sales of MM after Moog went under so it
might have been that they were just throwing down what they had to try to
get units out the door. 

James R. Coplin

***************************************
Work is the Curse of the Drinking Class
***************************************
  


> -----Original Message-----
> From: Csaba Zvekan [mailto:czvekan at gmail.com]
> Sent: Monday, June 16, 2008 1:49 PM
> To: James R. Coplin
> Subject: Re: [sdiy] Memorymoog VCO trim
> 
> James,
> 
> Did you use multiturn trimmers? Which ones are gold connectors ? Can
> you give me a link ?
> I have replaced all OP-AMPS, and 4000 series CMOS. And stability has
> been much better . Allthough I have one voice that never tunes in a
> cold state. Only when the MM+ runs for two days straight . I could
> press Autotune and get 6 voices tuned. Which I couldn't figure out
> what it is. I guess  I could replace the trimmer. That's a good idea.
> 
> Csaba
> 
> 
> On Jun 16, 2008, at 8:31 PM, James R. Coplin wrote:
> 
> > I had a similar issue with mine which spurred a massive overhaul a
> > couple of
> > years ago.  I replaced every cap in the synth, replaced all sockets,
> > headers, and connectors with new gold connectors, and had all new
> > cable
> > made.  I also replaced all the trimmers as mine were getting dead
> > spots.  It
> > took many, many hours but it sounds and tunes perfectly now.  I'm
> > glad I did
> > so I don't ever have to do it again...
> >
> > James R. Coplin
> >
> > ***************************************
> > Work is the Curse of the Drinking Class
> > ***************************************
> >
> >
> >
> >> -----Original Message-----
> >> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> >> bounces at dropmix.xs4all.nl] On Behalf Of Barry Klein
> >> Sent: Monday, June 16, 2008 1:02 PM
> >> To: synth-diy at dropmix.xs4all.nl
> >> Subject: [sdiy] Memorymoog VCO trim
> >>
> >> Hi all,
> >> I have been occasionally working on the MM+ I just purchased.
> >> Trying to get 6 tuned oscillators but only get 5.  When I go back to
> >> check
> >> usually I find one that is off by >2 digits from 7F.  Is that what
> >> would
> >> cause the tune failure or something else?  The oscillator that is
> off
> >> is not
> >> consistantly the same.  I also see a problem where every 6th note
> >> does
> >> not
> >> play in this test state.
> >>
> >> This is the 3rd MM I have worked on and (as before) the trimpot
> >> adjustments
> >> are damn touchy.  So much so that I wouldn't want to even bump one
> >> that
> >> was
> >> tuned....
> >> Is this due to old trimpots - do new ones make life much easier here?
> >> Anyone tried installing digital pot IC's?
> >> What improvements have you made to your MM's to either make
> >> calibration
> >> easier and more stable or even just mods you have made to increase
> >> capabilities?
> >>
> >> Barry
> >>
> >>
> >>
> >> _______________________________________________
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> >
> >
> >
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