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Scratching DPDT pot when not touching the strings

lifer_

lifer_

Oct 19, 2011
151
72
Bulgaria
#1
Hi,
I need an advice from where to start searching problem. Today I rewired my P/J with knew Bourns pots -volume and volume DPDT for passive/active, the tone control is EMG BTC. Also shielded the pickups and control cavities. Everything works fine, quiet as never before.
The thing is that when I'm not touching the strings or any ground the DPDT is scratching turning it in any direction. When I touch the strings everything stars to work great, no scratching at all. First I thought maybe I did cooked it, but then touched the string and the noise was gone.
I think it could be sort of a ground problem or cold solder. I've grounded it on the back of the switch, there was a lug for the purpose. Measuring the resistance between the pot and the strings shows 00.1 and even 00.0. Tomorrow I gonna check all connections again, especialy the grounding of this pot. I'm now just too tired to open the cavity again.
Is there a chance to be dirty pot, it's brand new?

Any ideas?
Please help
 
#2
Ok, so I checked every ground and signal connections around the pots. No problem with cold solder. The scratching is still there. I did a search and except the "dirty pot and clean it" answer, there is also "might be a DC in the circuit". I did some measurements and couldn't find any. Except the battery :).

The other thing was the lube in the pot. I found this:

"here's the long answer. in an effort to make really smooth feeling pots, the manufacturers use a non conductive lube on the shaft to bushing connection. this makes for an intermittent connection between the two metal pieces. if you are not touching any other metal parts on the guitar, you are intermittently getting connected to ground. i can't think of a real playing situation where you would not have either your left hand on the strings, or your right hand on the bridge, so i think the better feeling pot is a good compromise."

I tried with some plastic knob lying around and it worked fine. So not touching the metal shaft of the pot is the answer.

What do you think about that? Is there something that could help or to stick to plastic knobs :)?
 

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