[sdiy] Memorymoog pots

[Roman Sowa]

Deoxit won't help if the trace is worn out completely or if there's too 
much dirt. Open the pots, clean them and see how the trace looks like.
But before you do that, check them with a scope. Simple multimeter won't 
help here, you will not notice scratching spikes and noise. Then you can 
be sure which one to open and which one is still OK. I did that with all 
pots when it was too expensive to replace them or blindly open them all 
(over 100 Allen Bradley). Now I do that with every old pot ever since. 
If it's already tied to DC, it's super easy. Connect probe to the wiper 
and observe the scope at slow time base slowly turning the pot full 
rotation several times. Obviously digital scope in peak detect mode will 
work best here.
To check pots not tied to DC in the circuit, connect some 0.5V from 
external supply. 0.5V won't hurt anything in the circuit and it's good 
enough for scope test.

Roman

W dniu 2020-12-28 o 04:50, Barry Klein pisze:
> I left it on over dinner and came back and it read “5 out of 6 tuned”.  Hit Autotune and got 6 out of 6!  Played with pots and auto tune failed. I remember now that autotune will fail if the numbers are unstable. Maybe some deoxit and they’ll be good. But I’m not going there.  It’s playable for now.
>
> Sent from my iPhone
>
>> On Dec 27, 2020, at 7:18 PM, Michael E Caloroso <mec.forumreader at gmail.com> wrote:
>>
>> Get out the voltmeter and measure the wiper of the pots.  If reading
>> is steady then the pot is fine.  Otherwise you got a rogue component
>> somewhere, hard to find over the the internet.
>>
>> MC
>>
>>> On 12/27/20, Barry Klein <barryklein at cox.net> wrote:
>>> I took down a Memorymoog in its case from the garage rafters to check its
>>> condition. I was worried maybe the case foam melted into it by this time
>>> (maybe 7-10 years?). Case foam ok but several pot shafts are really wobbly,
>>> giving erroneous readings on the display.  What’s with this??? Might need
>>> source for new pots.  Doesn’t auto tune but sounds in tune when I play it.
>>> Another one I tried gets weird every 7th hit of a key and 5 out of 6 voices
>>> tuned.
>>> 3rd one is upstairs in my office, wrapped in protective foam.  Played nice a
>>> year or two ago.
>>> Dx7 needs new battery. I may install a backlit display while I’m at it.
>>> Life with hardware synths.
>>>
>>> Barry
>>>
>>>
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>
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