Fender's "Conductive" cavity paint... REALLY?!

[ux4484]

I recently recieved a loaded Strat pickguard via eBay (American Standard Alnico V's with an ACME toneshaper). Since the Mrs gave me my Blacktop, I had only taken off the rear plate (to add trem springs). I knew the Blacktop was a swimming pool route, but was surprised to see Fender's "Conductive" paint with a ground lug in the cavity. To accomodate the Toneshaper, I had to rotate the lug as it was hanging in the pot cavity. I noticed two things, first, the paint did not make it up the sides of the cavity (except near the controls), and secondly it was of varying thickness in the bottom of the cavity. On a lark, I tested it with my cheapo Harbor freight meter... Not conductive... Hmmm, got out my Good Fluke digital... even with some serious scratching... Very HiGH resistance from one side to the ground lug (and other areas). Not until I got out my old trusty Triplett model 60 (Analog) was I able to get a reading even close to a "conductive" reading (80-120 ohms). I was reaching for the copper tape... but I REALLY wanted to try the pups/shaper, so I wired it up and tried it out. Once strung and tuned, I immediately regretted not installing the tape. All but (already silent) positions 2 & 4 were very noisy *sigh*. At the least I should have put a strip from the lug up to the lip to hit the guard foil when installed. I think some locking tuners are required to make tweaking this setup easier.
Anyone else foiled over Fender's "sheilding"?

[sumgai]

ux,

+1 for using "foiled" in reference to shielding, that made me smile. ;D

But no, as ChrisK would put it, in his usual Zen manner: Conductive Paint Isn't.

By and large, it's a sop, meant to make the manufacturer look like they're doing something about buzzing/humming/noise, but in fact, it's only because it's dirt cheap that they're doing it at all. As I'm sure you're aware, installing copper tape (or even aluminum foil) isn't fast and easy*. But it is the only way to get the job done correctly. Many Nutz believe that the copper with conductive adhesive works as well as needed (no soldering required), but I haven't personally used it, so I can't say with authority that it's the best way to go. But ask newey, I think he's used it on one (or more) of his builds....

HTH




sumgai

* Leo had the better idea - using brass, make up ahead of time a cavity shield that looks like a tight-fitting tub. This was simply dropped into the body by the assembler, who then soldered a wire between it and the main grounding point. I don't think it was used on any other models besides the early 60's offset-waist guitars (Jazzmaster, Jaguar and Bass VI), but I've read elsewhere on the 'net that some of the newer re-issue models are also using this shielding method. Kind of surprising that not even the so-called boutique guitar makers do this.

[ux4484]

I've copper tape shielded 3 so far (Squier '51, Cortez Tele, and Fender JP-90 bass), all 3 were a marked improvement in hum reduction.
I was surprised the Blacktop had anything (having covered humbuckers). It had the cavity paint, and a full foil shield on the guard. The new guard is foiled, and the toneshaper has lugs for the jack ground and a second bigger lug they indicated should take the bridge and cavity ground together (if a cavity wire existed).
I did make sure the second lug had connectivity (as it were) to a couple spots on the cavity paint, but clearly it's noisier than my other SC guitars.
If I'm going to be playing with the toneshaper, I should probably put locking tuners on it to make tweaks faster. When I do that, I'm going to try a piece of copper tape from under the cavity lug to the lip under the guard and see if it helps, But I've got a bad feeling...

[ux4484]

May 29, 2013 16:08:07 GMT -5 ux4484 said:

I'm going to try a piece of copper tape from under the cavity lug to the lip under the guard and see if it helps.

I am amazed to say... this actually worked. A 1/2" wide, 3' long piece of copper tape, put under the cavity ground lug (screwed through it), up the side and over the top (right under the biggest foil area of the pickguard). I'm thinking when I rotated the lug to accommodate the toneshaper, the connection with the high resistance "conductive" paint suffered. Putting the tape under it and screwing through it gave me lower resistance from the lug to other parts of the cavity, and makes sure the foil on the guard is one (relatively) with the kind of conductive paint. The reduction in hum in positions 1, 3, and 5 is significant. It's not quite as significant as on my '51 or Tele, but both of those guitars do have humbuckers (in one or both positions). At least now, the hum is no longer driving me nuts. 

Weird thing about the bridge pup on this guard. It has two big screws in between the 1-2 and 5-6 poles. Researching: this is Fender's cheapo solution to putting a metal plate on the back of the pup (ala Callaham) to make it "hotter" (something we've discussed before).