Vintage Synth Repair

I use felt pipecleaners as you can bend them around contacts and they
absorb cleaning liquids.  But the best is to pullthe rodd and buff it on
the sort of machine a jeweller will have.  And rotate it if worn.

lorne

> The pitch changes as a key go down indicates a resistive connection
> between the contact and bus rod.  Often they are worn, sometimes damage
> through bad maintenance.  There are many ways to correct, some very
> imaginative to stupid.  The bus and contact have a thin gold plating,
> once worn off, problem area. 
>
>
> I remove the bus rod to allow better access to the keys side contact.  A
> good desoldering skill set is required as the plastic can be damaged by
> too much heat .  Sometime I just rotate it 90 degrees to give a new gold
> area to contact.  One guy told me he used unwaxedd, so dental floss wet
> with contact cleaner and sawed it back and forth.  Main thing, as the
> contact strikes, you do not want changes, as voltage equals pitch.
>
> Drill a hole in the pot with a small drill to allow pot spray to be shot 
> in. Insert the drill into the chuck so only an 1/8 inch sticks out, cut
> off or grind off if to long.  This prevent the drill from going to far
> into the pot and doing damage.  The metal is hard, so patience.
>
> R
>
>
>
>
>>________________________________
>> From: Gil <gilwe@...>
>>To: vintagesynthrepair@yahoogroups.com
>>Sent: Monday, July 9, 2012 8:40 AM
>>Subject: [vintagesynthrepair] Re: Minimoog D pitch drifting
>>
>>
>> 
>>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 !
>>>   > >
>>>   >
>>>
>>
>>
>>
>>
>>