Epoxy potting

[Bruce Johnson]

No, we pickup makers rarely meet up in person. Too many problems in the past.... Forbon in the beer pitchers, magnets in the peanut bowl, bobbin fights, and all that 42 ga wire tangled around the table legs. Most bars won't have us back. Even the bikers were complaining.

[David King]

Bruce!
I resemble this comment. What gives you the right to bring it out into the open? I suspect you've been drinking your own urethane cool-aid for too long.

[DialtonePickups]

After lots of trial and error, I/we've learned a few things. I'm posting here in case anyone else finds it helpful:

- I tried the West Systems epoxy a couple of times, and it broke both pickups. Something in that material must not work with our active circuit
- Johnson's wax is amazing. It works really well for managing the epoxy. And it smells good.
- I tried to use tacky glue on a section of the magnet wire, just out of curiosity. It broke the pickup.
- We used a "glue doctor" to find a new epoxy. I don't know the name, but the glue doctor was incredibly helpful in finding the right material.
- Now that we're using the right stuff, testing the pickup wet works just fine.

Thanks again for your earlier help, guys!

[big_teee]

What size and type of wire did the glue break?
I use a lot of 44SP and I've put hard as nail lacquer on it before to make it stay put.
Never any trubble!
T

[DialtonePickups]

What size and type of wire did the glue break?
I use a lot of 44SP and I've put hard as nail lacquer on it before to make it stay put.
Never any trubble!
T

I believe it's the regular old gold magnet wire, 44 AWG?

It's possible it wasn't the wire breaking that was the issue, but instead tacky glue getting somewhere on the circuit it shouldn't. It's sometimes hard to narrow down the cause of a problem in our pickups, because by the time we notice it or it sets in, the pickup is set in epoxy.

[Jason Rodgers]

I found working with 43 challenging, because I couldn't feel the damn stuff between my fingers. 44 is so thin, was the epoxy shrinking and breaking the wire? Or was it just a solvent getting into your electronics? Saying much more might reveal trade secrets. And what with your husband working for DARPA, you could tell us, but then I suppose you really could kill us.

[DialtonePickups]

I can feel the wire, no problem, but my eyes aren't the best so I can't always see it.

I've asked John not to tell me anything too sensitive about the pickups, because I know I have a big mouth, and will mistakenly give something I shouldn't away. Not that anyone who cares won't figure it out soon enough, but I'd hate to be the one to spill the beans.

I do think it could be the solvent on the electronics in this case, although the tacky glue did also seem pretty brittle for using with such thin magnet wire.

[big_teee]

You might try covering that area before the tacky glue.
I put copper foil tape on my bass pickups before I put anything on them.
GL,
T

[David King]

I've got to say I'm baffled to hear this as most modern day electronic components are going to be totally resistant to any reasonable potting material.
I have no idea what "tacky glue" is. Is that a brand name or a generic description?

Most of the copper foil tapes I've worked with are specifically for shielding and thus have a conductive adhesive which I wouldn't want to get on or need anything that could short out. I really like using the cheap old PTFE plumbers tape around my freshly wax-potted coils. It's 100% removable/reversible and won't react with anything for many centuries.

[big_teee]

I agree that you wouldn't want the copper foil where anything would short.
I use it for shielding and it does cover the wire, keeping it from glues and epoxy.
I use mainly paper and cloth tapes.
GL,
T

[Jazz P Bass]

I can feel the wire, no problem, but my eyes aren't the best so I can't always see it. .

With the pervalence of surface mount technology, I find using a magnifying visor a 'go to, gotta have' tool.



As they are available in different magnifying ranges, with changable lenses, you have to pick the best one for the application.

Headband Optivisors - Magnifiers - Jewelry Tools

[Joe Gwinn]

After lots of trial and error, I/we've learned a few things. I'm posting here in case anyone else finds it helpful:

- I tried the West Systems epoxy a couple of times, and it broke both pickups. Something in that material must not work with our active circuit
- Johnson's wax is amazing. It works really well for managing the epoxy. And it smells good.
- I tried to use tacky glue on a section of the magnet wire, just out of curiosity. It broke the pickup.
- We used a "glue doctor" to find a new epoxy. I don't know the name, but the glue doctor was incredibly helpful in finding the right material.
- Now that we're using the right stuff, testing the pickup wet works just fine.

Thanks again for your earlier help, guys!

What you found out is that the word "epoxy" covers a very broad range of materials, only some of which are designed to work for potting fine-wire coils. West Systems' materials are intended for making boat hulls and other fiberglass components.

One thing to note if making active pickups is that glass components, like some kinds of diode and reed-relay switches, tend to crack if potted in epoxy, with glass-epoxy contact. The standard fix is to pre-coat the glass part with a soft buffer coat of some kind. Urethane rubber and/or wax are traditional buffer materials.

[David King]

I keep getting email from this place and they will send out free samples.
Epoxies, Etc. ? Epoxies, Silicones & Urethane Formulator
They specialize in potting materials and will undoubtedly have something that would suit your needs at a price...

[DialtonePickups]

Thanks! The stuff we are using now seems to be working perfectly, but we'll take a look, free samples can never hurt.

[DialtonePickups]

I'll pass that on to John, thank you!! I just build the pickups following a long list of instructions, but I don't really know what each piece is/does. I'm not sure if he's accounted for this already.