Vintage Synth Repair

Hi all !

So I received it a week ago and did the following -
1. I took all PCB's out and cleaned the connectors
2. I rewires a few bad solder joints going to the pitch and modulation wheels
3. I cleaned the PCB sockets and checked for tight connectivity between the PCB's and flags
4. Replaced the 1458 ICs in the generic tuning circuit (where the Tune pot goes)

I see the tuning problem less then before but it still happens from time to time. I *think* it happens more when playing certain keys in the middle of the keyboard (although I don't see why it will only happen when playing this specific area). sometimes, the pitch will raise and fall as I push some keys down (like when using after-touch) - can bad kayboard PCB cause this ?

Also, in the specific machine, the master Tune potentiometer doesn't reflect the tune. The "default" tunning is a down that what it should be. The Tune pot shows correct resistance values when rotating it, and the soldering and connection to the sockets (and then PCB) looks ok... Which is weird. Also, tapping on the pot, it doesn't seem to reflect the tuning at all, as if it is dead... but it is not :/





--- In vintagesynthrepair@yahoogroups.com, "Paulo Palmieri" <paulopalmieri@...> wrote:
>
> That´s right. To affect the 3 oscillators maybe the countour generator could be the problem or the PCB conectors already commented here.
> This is the late version more stable than the first generation.
> 
> Good luck and be in touch!
> 
> Paulo Palmieri
> 
> 
>   ----- Original Message ----- 
>   From: Quazimodo 
>   To: vintagesynthrepair@yahoogroups.com 
>   Sent: Friday, June 29, 2012 4:51 PM
>   Subject: [vintagesynthrepair] Re: Minimoog D pitch drifting
> 
> 
>     
>   So it's a late, *stable* one... OK, then it will probably be much like I said in the first place.
> 
>   Check those flags...!
> 
>   --- In vintagesynthrepair@yahoogroups.com, "Gil" <gilwe@> wrote:
>   >
>   > 
>   > Thanks. Serial is 12044. Supposed to get it in a few days so I'll be able to tell what it exactly uses (or do you know be the serial number?)
>   > 
>   > 
>   > --- In vintagesynthrepair@yahoogroups.com, "Paulo Palmieri" <paulopalmieri@> wrote:
>   > >
>   > > Hi Gil,
>   > > 
>   > > Probably there is a variation in the cv voltage that controls the oscillators.
>   > > I experienced similar issues on the osc 1 of a RA Moog model (the first earlier version) and the only thing that solved the problem was replacing the 2n4058 transistors.
>   > > Please, provide more info such like serial number and if your oscillator board has only transistors or 2 ICS SG3821 or CA/LM3046 or 3 UA726 ICs.
>   > > 
>   > > Regards,
>   > > 
>   > > Paulo Palmieri
>   > > 
>   > > 
>   > > ----- Original Message ----- 
>   > > From: Gil 
>   > > To: vintagesynthrepair@yahoogroups.com 
>   > > Sent: Thursday, June 28, 2012 9:55 AM
>   > > Subject: [vintagesynthrepair] Minimoog D pitch drifting
>   > > 
>   > > 
>   > > 
>   > > 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 !
>   > >
>   >
>