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Vintage threads from the first ten years

Potting Pickups

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8/23/1999 1:18 PM
Mook	Potting Pickups Hey I have some Seth Lovers 'buckers that squeal at higher volumes. I've been told to get them potted. I understand this basically means dipping them in melted parafin. Does this change the sound? What does potting do to the tonality of the pickup? Thanks, Mook

8/23/1999 8:39 PM

The only change in tonality is removal of the vibrational feedback. Some players use the queal to their advantage, but to most folks it's a nuisance we can gladly do without. (I think the metal cover has more noticeable effect on general tonality than wax potting.)

You can easily pot these pickups yourself, when your wife is out of the house. The best mixture is appx. 20% beeswax + 80% paraffin (candle wax), but 100& paraffin should be fine in all but coolest climates. (You'll need to remove the metal pickup cover prior to potting the coils.) Melt some wax in a metal or glass container that's sitting in a pot containing water near the boiling point (called a double boiler in cooking circles). Immerse the pickup in the liquid wax, and leave it there until it's completely penetrated. If the pickup is not up to temperature, let it sit in the bath until it's warm enough to allow the wax to flow completely throughout. What I do, after I pull the pickup from the bath, is blow a hair dryer on it to remelt the wax and catch any excess that drips off in paper towel blotters. You can wipe much of the excess wax from the face of the bobbins with paper towel. After cool, resolder the cover in place.

8/24/1999 8:50 AM

Doc:

100% paraffin should be fine in all but coolest climates...

I thought that it was the hot climates that had the problem... In any case I just wanted to add that you should leave the pickup in the melted wax for at least an hour. I'm not sure if that will solve the squeals because I understand that the manufacturers use a pressure or vaccuum process to ensure that the wax penetrates all of the windings. But I do it to all of my pickups anyway...

Thanks!

Steve Ahola

8/24/1999 3:03 PM

Steve:

I was under the impression that the beeswax doping, beeswax being softer at room temperature than straight paraffin, allowed the wax potting compound to become less brittle under cooler temperatures. Someone stated (possibly Mark H?) that breaks could occur in the winding when using the straight paraffin, that's why they recommend beeswax addition. Maybe it was from Lindy Fralin? Anyway, it made sense to me, but I have no direct experience.

Beeswax is more expensive, and obviously less plentiful than petroleum products, so the 20% proportion was probably the economical blend giving the desired resistance to brittle fracture.

Doc

8/24/1999 3:36 PM
Gus	The 20% b 80% p is from a stew mac cat. I think Stew Mac has the article up at there web site now. The 20/80 is to minimize the stress on the wires. I read somewhere epoxy potting can sometimes cause the wires to break with big temp changes

8/24/1999 6:08 PM

Doc:

I was just checking the Donald Brosnac book on Guitar Electronics and regular parafin melts at 130 to 140 degrees. Synthetic beeswax (made by synthetic bees?) melts at 170 degrees. And if you are trying to pot a humbucker the plastic bobbins can melt at 140 to 150 degrees. So he recommends plain old parafin for the humbuckers and synthetic beeswax for strat pickups.

So if there is cloth tape on the hb coils would you remove that carefully before potting the coils? Or just figure that the wax will soak through...

Steve Ahola

P.S. I'd heard stories of guitarists playing down in the Southwest who had the parafin from their pickups melt out and get all over everything. (Guitars in a locked car on a hot day could easily get to 150 degrees or higher.) But I also see your point about the wax flaking off if it was too cold...

8/24/1999 7:28 PM

Bear in mind that besides making excellent radio antennas, pickup coils also serve nicely as heat sinks. Unless the ambient temperature is quite substantial, it is hard to see how the wax embedded in a pickup coil will succumb immediately to a warm environment without having that external heat tempered by all that copper and alnico.

Even where it does, remember that the purpose of wax potting is not to assure that every available micron of gap is filled up by wax, but to assure that individual turns aren't bouncing around against each other, and egged on by sympathetic vibrations from the speaker. Throw a ping-pong ball into an enclosed space with hard walls all around and it keeps rebounding. Throw the same ball into a space with one wall covered by a deep pile shag rug and the bouncing attenuates much more abruptly. Certainly covering all walls with shag rug will kill rebound immediately, but covering one wall will make an immediately noticeable difference wih least effort. Similarly, stick your finger beside a freely vibrating string and it stops vibrating very soon without you having to squeeze the string on both sides. If there is a bit of wax near any loose turns, that should dampen vibrations and keep microphonics to a minimum. More wax isn't harmful, but doesn't necessarily make that big a difference. If anything, the inner layers should be largely impenetrable, and held firmly in place by outer layers, so all you really need is a bit of wax on the outside.

To my mind, the chief concerns of wax potting should be:

1) avoiding any damage to the coil itself

2) avoiding damage to yourself and property (and marriage)

3) not having a thick superficial layer of wax fall off the next day leaving nothing in the coil.

As long as the coil is responsibly wound, SOME wax gets in there, and the coil is snugly wrapped afterwards, I should think one would be home free with respect to microphonics (iron filings and ferrous particles notwithstanding).

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