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Re: Conductive Paint

5/6/1998 5:47 PM
John Greene
Re: Conductive Paint
Copper and conductive paint work but steel would be better (by the way, steel "foil" is available as shim stock from McMaster-Carr supply company, actually so is copper, brass, aluminum, stainless steel, etc., etc.).  
I recently shielded my Strat. I have a Deluxe Strat Plus that originally had Lace Sensors and I installed Texas Specials. The Texas Specials were *much* noisier that the Lace Sensors but sound mucho better. Anyway, I went the route of getting copper foil with adhesive back and lined the entire cavity. I soldered all the seams but not completely along the entire length, just at points that would insure connection and provide support for anything that could come loose. The result was excellent, it's completely quiet. The pickguard already had a sheet of adhesive backed aluminum foil stuck to it.  
If I'm going the conductive-paint route use the water based type not the MEK stuff.  
I wanted to just use conductive paint as it would have been much less work. However, I heard an arguement against using the carbon conductive paint (which is all I could get locally). The problem was that it could be disolved too easily by pot-cleaning stuff, guitar polish, whatever. The recommended paint was nickel paint that has a laquer base. I think it's available from GC Electronics.
5/7/1998 6:09 PM

Wasn't your Strat Plus pickup caity already coated with shielding paint from the factory? So far, every Am Std strat I've been in has shielding paint. I don't know if it's carbon or metallic based, but it's under the final clear coat. There's a ground lug screwed into the paint. The sheet metal screw cuts thru the insulated clear and makes contact with the conductive paint.  
Maybe yours was shielded with paint, but the copper foil did a better job of hum reduction with the single coils?  
5/7/1998 10:01 PM
John Greene

I saw the ground lug screwed into the paint and thought it was pretty stupid to screw a ground lead into the wood. Now it makes sense. Maybe the screw wasn't making very good contact.  
It didn't work very well at all. The copper did a much better job of shielding as it went from always being noisy to being more quiet than it was with the Lace Sensors. Even with the Lace Sensors I would get hum if the guitar was at certain angles.  
I made sure that the copper foil lapped over the edge of the cavity a little so it would make contact with the aluminum foil already stuck to the pickguard. Maybe that had something to do with it.  
5/9/1998 5:02 PM
Steve A.

But I have still have two questions. 1st, where does the 2.2uF cap connect to?  
After tying all of your signal returns to a star ground point (which goes to the output jack ground) you connect the shield grounds, string ground, pot cases, et al, to that point through something like a 2.2uF/250+volt polyester cap. The idea is to isolate the "chassis" grounds from the signal returns through that large valued capacitor.  
This idea came from John Natchley's web page which suddenly disappeared a few months ago. He is evidentally an engineering type who started working on guitars a few years ago and redesigned the ground paths for a strat-style guitar using basic electronic principles for AF and RF circuitry.  
The idea of isolating the string ground from the output jack with a capacitor has been around for many years as a SAFETY mod (to prevent electrocution) but Mr. Natchley suggested that it would also reduce noise and hum. Since I did all of the shielding mods at the same time, I can't say how much the capacitor helped (I could go back and bypass the cap with a jumper to see if there is any difference).  
In any case, his web page did open a lot of eyes before it disappeared. I had always designed my guitar harnesses using ground paths and signal returns interchangeably.  
Steve Ahola
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