Vintage Synth Repair

There are basically two Minis, the later Moog (Norlin then owned Moog) being more adjustable and tracks better on the hi end, because of the extra VCO adjustment. They sent out kits to convert to the later more trackable VCOs back in the day.  You had to drill extra holes in the back cover to make the new adjustments to the VCOs.   


There are mods to reduce tune drift and to create a dead or off zone in the bender.  Both models drift a few cents here or there.  But your steps and I assume all 3 VCOs drift in unison.  This suggests some common item like the bender pot or an unstable supply voltage.  




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> From: Gil <gilwe@...>
>To: vintagesynthrepair@yahoogroups.com 
>Sent: Thursday, June 28, 2012 5:55 AM
>Subject: [vintagesynthrepair] Minimoog D pitch drifting
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>I'm handling a friend's mini, which acts strangely. The overall pitch (of the entire machine) will change suddenly, up and down, not to far from the correct pitch but a few semitones... It affects all oscillators at the same time. Is this a known issue in old minimoogs? I would usually suspect either power supply main voltage instability, bad caps or transistors, but being it affecting all 3 oscillators, I tend to think it is not oscillator circuit related ? :/ I'm new to minimoogs so any help would be appreciated... Thanks !
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