Potting Pickups with something other than wax.

[Mike Sulzer]

And the last two:
r9.pdf r8.pdf

[big_teee]

What would happen now if you Wax pot it again, after the water test.
Maybe warm it up with a hair dryer, and remove the wax tape.
Then wax pot it with full penetration, then test it again?
Would that change it some more?

[Mike Sulzer]

I am thinking if you wax pot it really well, the water should not penetrate much, and the effect should be reduced, recovering quickly. I have never been a wax potter; guess I need some beeswax and paraffin. There is a hive right outside, but those bastards are more interested in stinging me and exciting my allergy than contributing to an experiment. I suspect that candle wax is the wrong stuff, too stiff.

What would happen now if you Wax pot it again, after the water test.
Maybe warm it up with a hair dryer, and remove the wax tape.
Then wax pot it with full penetration, then test it again?
Would that change it some more?

[Bruce Johnson]

Yeah, I read Leo's Patent to be mostly about solving the problem of moisture soaking into an unpotted pickup. Soaking it in wax drives out the moisture and the air in between the wires, and fills the gap with wax, preventing moisture from getting back in. And it makes sense that an unpotted coil soaked with water would have a significantly different capacitance.

But it still seems to me that residual moisture from using a water-based potting material will cause much less of a capacitance change than that, probably negligible. Assuming that I can get the polyurethane to fully seep into the coil, almost all of the space between the wires will be filled with polyurethane. So, the dielectric properties of the polyurethane should drive the capacitance.

I'm going to try potting some coils this week with the Target EM9000, and compare them to the coils that I normally pot with CPES epoxy.

[David Schwab]

I used to pot with non water based polyurethane, and on the coils that I cut off the bobbin, it didn't soak all the way through the coil, and it also never fully dried. I stopped using it because it sometimes left them microphonic. Plus it was a slow process since I had to leave them to dry over night.

My wax potted coils are fully impregnated, and I don't even use a vacuum.

[Joe Gwinn]

What would happen now if you Wax pot it again, after the water test.
Maybe warm it up with a hair dryer, and remove the wax tape.
Then wax pot it with full penetration, then test it again?
Would that change it some more?

If you pot with moisture in the coil, you may well trap the moisture. Better to fully dry before wax potting.

[Joe Gwinn]

I am thinking if you wax pot it really well, the water should not penetrate much, and the effect should be reduced, recovering quickly. I have never been a wax potter; guess I need some beeswax and paraffin. There is a hive right outside, but those bastards are more interested in stinging me and exciting my allergy than contributing to an experiment. I suspect that candle wax is the wrong stuff, too stiff.

Smoke them.

[Joe Gwinn]

I used to pot with non water based polyurethane, and on the coils that I cut off the bobbin, it didn't soak all the way through the coil, and it also never fully dried. I stopped using it because it sometimes left them microphonic. Plus it was a slow process since I had to leave them to dry over night.

One-part urethanes require access to the atmosphere, which will be slowly in this case, with all that fine copper wire in the way.

Catalyzed epoxies need not have contact with the atmosphere to cure, and so have no problem curing all the way through.

And wax needs no air access either.

[Mike Sulzer]

What would happen now if you Wax pot it again, after the water test.
Maybe warm it up with a hair dryer, and remove the wax tape.
Then wax pot it with full penetration, then test it again?
Would that change it some more?

I pulled the tape off; you could see that it had been lightly wax potted over the tape, but there was no penetration into the wire. I melted some votive candles and left the pickup in for three hours. (I have no vacuum.) Compared to before the potting, the impedance changes less when the pickup is in the distilled water, and the recovery to something close to before putting it in the water is quick, but there is still some residual effect. (I did this on the day tropical storm Bertha passed by, and it was a lot cooler than normal; this affects the dc resistance compared to the measurements before. It also affects the height of the resonant peak since a lower resistance means a higher peak.)

waxedinwater.pdf waxeddry.pdf wr1.pdf

[Mike Sulzer]

There is also an issue with the capacitance on the plots. This is derived using a model including some free eddy current parameters and is derived using data from high frequencies only. However, the model does not know about extra loss from the water, and so the derived capacitance is not correct when there is water present.

I pulled the tape off; you could see that it had been lightly wax potted over the tape, but there was no penetration into the wire. I melted some votive candles and left the pickup in for three hours. (I have no vacuum.) Compared to before the potting, the impedance changes less when the pickup is in the distilled water, and the recovery to something close to before putting it in the water is quick, but there is still some residual effect. (I did this on the day tropical storm Bertha passed by, and it was a lot cooler than normal; this affects the dc resistance compared to the measurements before. It also affects the height of the resonant peak since a lower resistance means a higher peak.)

[ATTACH]29895[/ATTACH] [ATTACH]29894[/ATTACH] [ATTACH]29896[/ATTACH]

[David Schwab]

One-part urethanes require access to the atmosphere, which will be slowly in this case, with all that fine copper wire in the way.

Catalyzed epoxies need not have contact with the atmosphere to cure, and so have no problem curing all the way through.

And wax needs no air access either.

I've tried not wax potting them at all, since I encapsulate the pickups in potting epoxy. But on a pickup that was microphonic, I cut it apart and the epoxy never got all the way in the coil. It might if I put them in a vacuum.

Of all the things I tried, wax is the easiest, fastest and most dependable.

An alternative to potting pickups is to get bondable magnet wire.

[Joe Gwinn]

I've tried not wax potting them at all, since I encapsulate the pickups in potting epoxy. But on a pickup that was microphonic, I cut it apart and the epoxy never got all the way in the coil. It might if I put them in a vacuum.

The epoxy may be too thick. There are some pretty thin epoxies available.

Vacuum will certainly help. So will using slow-cure material and warming the pickup.

Of all the things I tried, wax is the easiest, fastest and most dependable.

An alternative to potting pickups is to get bondable magnet wire.

Bondable magnet wire will not keep the moisture out. While one can wax a bondable wire assembly, it seems like a lot of work - just use ordinary wire and wax it.

Another alternative is wax the coils, then epoxy pot the whole thing. This will work if the assembly is going into a shell of some kind. Epoxy will not wet the wax, but in a shell it doesn't have to.

[David Schwab]

The epoxy may be too thick. There are some pretty thin epoxies available.

Vacuum will certainly help. So will using slow-cure material and warming the pickup.

It's pretty thin, and is slow curing. Takes 24 hours unless you heat it up.

Bondable magnet wire will not keep the moisture out. While one can wax a bondable wire assembly, it seems like a lot of work - just use ordinary wire and wax it.

Exactly. Fender seemed to have used bondable wire on bass pickups at one point.

Another alternative is wax the coils, then epoxy pot the whole thing. This will work if the assembly is going into a shell of some kind. Epoxy will not wet the wax, but in a shell it doesn't have to.

That's what I do. I wax the coils, assemble the pickup, and then encapsulate the whole thing.

[Sinster]

Can I assume this is paraffin? Since it's not listed as such and it's 3.99 for the pound.,

[David Schwab]

The melting point on that is 148° F. This is the problem I had with some candle wax. The melting point was too high and it wouldn't melt very well.

I like to buy the paraffin used for paraffin wax baths that people stick their hands in:

Amazon.com : PARAMED Paraffin Wax Refill Unscented 6 lbs. Qty of 1 : Paraffin Baths : Beauty