Adventures in P90's, hum and dummy coils

RVA said:
I saw 3 guitars with 3 pickups in them at a local GC today. Let me know which ones you want

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I think I'm good for now Ray, Thanks.
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But that Supro excites me...
 
Hackmaster said:
I have given up on the treble bleeds, the only change that I noticed was I picked up all kinds of hum with the jumper wires.
I tried. Gonna live with what I have for a while. It works. The ability to switch the coil on and off will give me enough options to keep me
amused for a while.
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The problem here, is that the jumper wires can act like antennas and be more vulnerable to interference. Once you properly minimize the leads of the treble bleed circuit, and install them in between the pot's lugs, it should barely if any, add any interference. You did an excellent job with the dummy coil. You owe it to yourself to reapply the treble circuit properly and then judge it for what it can do.
 
Hackmaster said:
I've been tinkering again with a bag of P90's and an old guitar.
Some of you have seen my double cut triple pickup perversion posted elsewhere on this fine forum.
Well now I'll address an issue that I've been dealing with, hum.

The pickups that are in the guitar were stock Gibson P90s.
I found another P90 that when added in with the stock pickups, squelched most of the hum.
I added that one to the middle position, and wired it up with the neck & bridge pickups going thru the 3 way switch to one volume & tone pot, and the middle pickup to the other volume & tone pot.

Now with all three pickups on, everything was pretty quiet. The problem surfaced when I would turn down the middle or the neck & bridge set, the hum would increase as the pickup was turned down.
This is fine if you want all three pickups on all the way all the time, or combinations of neck & middle or bridge & middle on all the time.
If you turned both volumes down the same amount, the hum would also be squelched.
Gettin' complicated now.

This would not do...

So I did some research and armed my self with just enough information to make me dangerous and reckless.
The article that I referred to...
Dummy Pickup Coils for Single Coil Powered Guitars

So utilizing one of the pickups of a Precision Bass set,
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I removed the plastic cover, ripped off the magnet and checked to make sure that the
wind direction was correct to achieve the hum canceling. Bingo! Quiet as a church mouse.
So I took this hapless little pickup and ground the square edges off one end and covered both sides with epoxy.
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Then put a shrink wrap sleeve over the whole thing.
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I hooked it up to engage with a push pull pot so that I would reap the most benefit from the addition.
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It adds the coil between the output going to the jack and ground.
Everything fits nicely in the corner of the control cavity.
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Now your probably thinking how is that idiot going to keep that coil from flopping around in that control
cavity? The cavity was getting pretty crowded now, I thought about a piece of stiff foam, but that would have
to be cut to the proper shape & thickness to work well.
So I searched for my answer from above... No I'm not getting religious on everyone.
Remember the plastic cover originally on the donor pickup?
It makes a good source of stock to make a nifty little angle bracket out of
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that got epoxied to the underside of the cavity cover.
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The cover fits on with no interference and no one sees anything from the outside of the guitar.
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Now for a proper daylight picture of the conversion...
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I just may add it direct so that the dummy coil is on all the time, but I thought the push pull would give me
a chance to compare the tone with and without the addition of the dummy coil.

If any of our more knowledgeable wiring and tone gurus would like to comment pro or con on this little
addition, I'd love to know your thoughts. Feel free to let me have it with both barrels.:D
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One of the biggest problems, it that you need to shield the entire inside of the guitar, and the wiring you use inside should also be shielded wire.
The inside should be painted with 3 coats of shielding paint, and use pipe cleaners to coat the inside of the wiring holes.

The best shielding paint will contain Nickel.
This metal is one of the best for blocking external magnetic fields (which is the source of interference noise).

Shielding is always better when it is in multiple layers.
Two types of material (like copper and nickel) will work much better than a single layer of one material.

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Then you will lay in copper foil (not aluminum) on top of the paint.
On advantage of copper is that you can solder the overlapped ends together...
and you can solder ground connections to the shield.

Dummy Coil:
The coil should be the same as the pickups, the phase is reversed from the pickups, and it is in series with the pickups.
But this still doesn't change the need for shielding inside the guitar.
Then last, put your controls back in.

If you do all that there will be a major improvement. Like night and day...
 
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syscokid said:
There are copper shielding tapes where they are still conductive through the adhesive side of the tape. Therefore, no need to solder the overlapped ends together... which would definitely be great news for eESGe... :p

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I would rather solder the ends.
The adhesive breaks down over time, and I would like to make it permanent if possible.
I would raher use Mu metal foil instead of copper...but I think Mu metal is going to get on the expensive side...
Mu metal is 77% nickel, 16% iron, 5% copper, and 2% chromium or molybdenum.

All Products Catalog | Magnetic Shield Corporation

custommagneticshielding.magneticshield.com custommagneticshielding.magneticshield.com
 
Amp Mad Scientist said:
I would rather solder the ends.
The adhesive breaks down over time, and I would like to make it permanent if possible.
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I guess it's better to be safe than sorry. But in my own experience, I have at least one guitar where the control cavity was shielded ten years ago with conductive adhesive copper tape, and there are absolutely no signs of the tape edges coming up. And I also generously overlap the tape, so that might have something to do with keeping it stable too.
 
Almost gave up on the 2020 Gibson Special ,by far the nicest guitar i ever owned..its flawless..read some stuff where they put some care on em during the making. Anyways,,the latest kick.. wasn't getting what i wanted in the Marshall run with the 90's..yesterday put it in gain chan of the Mesa f100..there it was..the Mesa brought the Goldtop & Sg's back into play where the V's & Shredders with all the Dif SD & Dimarzio pickups really were best at hitting the Marshall's better in the font end. Pretty cool to use the 90's agian..they do have the snarl..almost traded the Sg the other day..phew... had the SG in the f100 on chan 2 with gain on 10 o'clock, treble noon, mid 11 o'clock, bass 9 o'clock..instant Black Sabbath Sabotage tone.. so darn close put Hole in the Sky on just to see
 
BFT Gibson said:
Almost gave up on the 2020 Gibson Special ,by far the nicest guitar i ever owned..its flawless..read some stuff where they put some care on em during the making. Anyways,,the latest kick.. wasn't getting what i wanted in the Marshall run with the 90's..yesterday put it in gain chan of the Mesa f100..there it was..the Mesa brought the Goldtop & Sg's back into play where the V's & Shredders with all the Dif SD & Dimarzio pickups really were best at hitting the Marshall's better in the font end. Pretty cool to use the 90's agian..they do have the snarl..almost traded the Sg the other day..phew... had the SG in the f100 on chan 2 with gain on 10 o'clock, treble noon, mid 11 o'clock, bass 9 o'clock..instant Black Sabbath Sabotage tone.. so darn close put Hole in the Sky on just to see
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I bought my LP Special specifically for that Iommi-style neck pickup thing. It's a fun guitar and I agree, it's basically flawless. Except the silly vintage-style white button tuners - those had to go, so mine has a set of Kluson Revolutions on it now. Anyway, yeah, lots of fun and a sound you can only get with P-90's, but I will say that if I was still gigging this guitar would never get used because of the hum.
 
syscokid said:
"Permeablity": So Mumetal is 20,000 times more capable of stopping interference? But Mumetal is only 3% as conductive as copper? I'm very confused... :run:
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It's not the conductivity that blocks interference.
Some materials absorb and dissipate the noise and some reflect the noise.
Some materials don't even need to be grounded to block the magnetic fields.
The noise comes from magnetic fields.
Like the magnetic fields around wiring inside the walls. Or the magnetic field of the amp's power transformer.
 
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