Vintage Synth Repair

Hi Group (especially Tom),

I can get a Polymoog for a fair price, but I'm told the oscillators 
are "unstable". Is this an easy fix? I'm getting the schematics w/ 
the synth.

Thanks for any help,
Scott

In a message dated 11/4/2002 4:03:54 PM Eastern Standard Time, thom_s4@... writes:

> I can get a Polymoog for a fair price, but I'm told the oscillators 
> are "unstable". Is this an easy fix? I'm getting the 
> schematics w/ 
> the synth.

In this instance, unstable means that they drift with temperature.  The power supply has been updated so as not to be marginal, although that was before I owned the synth.  Hope that helps with anyone who was pondering a reply...

-Craig

--- In vintagesynthrepair@y..., "tsomneevich" <thom_s4@h...> wrote:
> 
> Hi Group (especially Tom),
> 
> I can get a Polymoog for a fair price, but I'm told the oscillators 
> are "unstable". Is this an easy fix? I'm getting the schematics w/ 
> the synth.
> 
> Thanks for any help,
> Scott

Hi Scott!
 
As far as my Polymoog (Model 280) is concerned, there shouldn't be 
problems with oscillator instability.
Basically, as the Polymoog is no "classical" synth, there are only two 
oscillators which are divided down internally.
So the tone generation resembles more the "Hammond-principle".
Anyway, there were severe problems with my unit concerning operational 
amplifiers and some standard TTL circuits. There are actually hundreds 
of them!
The worst problem was with one of the two divider networks. As I 
couldn't get the genuine part, I had to replace it with a "home grown" 
substitute network.
So the schematics are essentially for future maintenance.
I'd be glad to help you with any advice when it comes to repairing...
 
Cheers,
 
Reinhard