# SHIELDING...electronics PITA



## greco (Jul 15, 2007)

*Just a warning to check to see if the control cavity is painted with conductive shielding paint before you do any changes of components *(replacing pots would be likely be the primary problem). 

I just wasted hours on rewiring, testing, etc. only to discover that the terminals on the new push-pull pots were shorting to ground due to contact with the shielding paint. Meter readings were going nuts once the pots were installed but were fine after I did wiring and before I attached the pots to the body (that should have been my first clue...DOH!) 

These pots were in recessed, drilled out portions of the control cavity. The edge/shoulder of the recess was causing the problem.

Solution: Logically...put something non-conductive between the pot terminals and the conductive paint. One could also likely sand off some of the paint, but this was not my guitar and I didn't want go that direction. I'm not sure how difficult it is to remove the paint to a level where it stops conducting.

Anyone else been through this agonizing wiring "discovery"? 

Comments?


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## Axeman16 (Jun 5, 2008)

generally you need to ground the shielding paint to the bus ground using an eyelet or lug. or you could put some electrical tape between the pot and point of contact but the eyelet would be ideal.


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## greco (Jul 15, 2007)

Axeman16 said:


> generally you need to ground the shielding paint to the bus ground using an eyelet or lug. or you could put some electrical tape between the pot and point of contact but the eyelet would be ideal.


The shielding paint is also/already grounded via the metal components (pots, switch, jack) that touch it...Correct?

I did use electrical tape (as you mention) between the hot and middle terminals of the pots
and the shielding paint.


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## Axeman16 (Jun 5, 2008)

well youd think yes. ive always used an eyelet as a safety but never have had an issue.did the tape solve it?


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## greco (Jul 15, 2007)

Axeman16 said:


> well youd think yes. ive always used an eyelet as a safety but never have had an issue.did the tape solve it?


Yes, the tape solved it.


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## knight_yyz (Mar 14, 2015)

I used a bottle of shielding paint on my Epiphone Black Beauty. Fred Gabrsek said he had to sand some off because it was causing a short in the guitar as well. I'm not worried about it as it is humbuckers in there, but since I had it apart and had the paint, I figured I might as well use it. 
There is also liquid electrical tape that may work better than sticky tape. Or if it is actually the pot causing the problem, you can buy plastic dust covers for the pots.


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## greco (Jul 15, 2007)

knight_yyz said:


> Or if it is actually the pot causing the problem, you can buy plastic dust covers for the pots.


Does the dust cover for the pots also cover the pot terminals? I can't see how that would be done, especially when the terminals have wires soldered to them. Any pics of that?


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## knight_yyz (Mar 14, 2015)

No, they just cover the round part. There are a few things you can use to coat the terminals. I have something from 3m, but it is a spray. I use it on the exposed circuit boards when I make pedals. Just in case the board moves and one of the legs of a component hit the metal box. There is liquid electric tape as well. Paint it on with a small brush and it is electrical tape without the glue


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## greco (Jul 15, 2007)

knight_yyz said:


> There is liquid electric tape as well. Paint it on with a small brush and it is electrical tape without the glue


This looks like it could be very handy to have around! 
Where do you purchase it from?

I was considering using nail polish but wasn't sure how well it would work. I then considered silicone, but finally just went with good, old, trusty electrical tape.


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## gtone (Nov 1, 2009)

Or you could just bend the tabs/terminal connections "up" so they're not making contact with the shielding paint. Just a thought...


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## greco (Jul 15, 2007)

gtone said:


> Or you could just bend the tabs/terminal connections "up" so they're not making contact with the shielding paint. Just a thought...


The pot terminals were touching at the point at about where they bend to enter the pot. I did give that immediate consideration as it is the easiest solution. I have also snapped one of those terminal connections off in the past, even with gentle bending...so I didn't want to repeat that mistake/bad luck. In addition, the terminals on push-pull pots are even more "delicate" than on larger pots.


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## Taylor (Oct 31, 2014)

2 weeks or so ago, I rewired an entire import Les Paul-style with full size pots and had an issue with shorting from the lugs contacting the shielding paint. (Of course, I'd already taken the entire guitar apart 3 times by the time I figured that out.) I ended up putting heat-shrink tubing over the wires and lugs, but clear nail polish should work, as would acrylic caulks and any latex or acrylic paint. I suspect that MOST silicone caulk should work, but since much of it is tin-catalyzed, it may be too highly conductive in a thin application, though I haven't checked. Electrical tape is a practical, simple, and reversible solution, as well.


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## greco (Jul 15, 2007)

Taylor said:


> Of course, I'd already taken the entire guitar apart 3 times by the time I figured that out.
> 
> I ended up putting heat-shrink tubing over the wires and lugs....
> 
> Electrical tape is a practical, simple, and reversible solution, as well.


I totally sympathize, taking everything apart (especially more than once) to try and figure out the source of the problem annoying and frustrating!!!

I might just unsolder the wires and put shrink tube "boots" on the terminals. I have to put a new switch in anyways (owners request) and shrink tube always has such a nice, professional look. Electrical tape works, but I think shrink tubing is better. Thanks for the idea. I saw that done by a luthier that rewired John Scofield's guitar but I had forgotten about it.

Cheers

Dave


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