Emergency potting

[fieldwrangler]

Folks -

Any good ideas on how to pot a pickup quickly and firmly? Can’t wax pot these; bobbins have glue joints that will give up with heat. Ultra-thin CA seems like it would get hot enough to melt wire insulation.

Does lacquer work? Never actually used it. If so, is there a good formulation grabbable at a hardware store?

Other ideas?

Bob Palmieri

[J M Fahey]

bobbins have glue joints that will give up with heat.

Are they homemade? ... What specific glue did you use? ... did you use hobby/craft specs hot glue?
Please post a couple bobbin pictures showing joints/assembly.

[fieldwrangler]

Thanks Juan! Joints aren’t visible; covered by windings. I used Master Glue Thin Cyanoacrylate for bonding circuit board to rubber flexmag

[Bloomfield]

I've heard of shellac being used but can't verify the results.

[Chuck H]

I'd be wary of using anything that requires evaporation to harden. Think about it... Once it skins over it acts like it's own container keeping air replenishment and circulation away from the still wet product inside. Maybe there's a thin catalyzed product you could use.

[fieldwrangler]

I'd be wary of using anything that requires evaporation to harden. Think about it... Once it skins over it acts like it's own container keeping air replenishment and circulation away from the still wet product inside. Maybe there's a thin catalyzed product you could use.

Man... thanks for this informed perspective - I really know nothing about such matters.

[Helmholtz]

I'd be wary of using anything that requires evaporation to harden.

That^^.
And the aggressive solvents used especially with lacquer may melt the wire insulation and cause shorts.

Pure paraffin melts below 60°C and thus allows for a relatively low potting temperature. I don't think there needs to be a risk for cyanoacrylate glue joints.

Ultra-thin CA seems like it would get hot enough to melt wire insulation.

What's your information about related reaction temperatures?

[copperheadroads]

I wax pot pickups all the time that is superglued together with never any problem .

[David King]

CA glue is one of the higher temp glues available to us so as long as you keep your wax below it's open air combustion temp you won't have any problems.
That said if you want to avoid the heat altogether then use a penetrating epoxy formula which seems to work perfectly for potting pickups. Epoxies.com sells many different potting epoxies that would also work well. Most conventional epoxies have superb penetrating capabilities as long as they are slower setting types. 5 minute epoxy is not what you want here.

[big_teee]

I agree with Copper and DK, you can wax pot super glue pickups.
I've made lots of pickups with bobbins glued to home brew baseplates.
I wax pot all of them.
Keep your wax temp 150F or less, and you should have no problems.
T

[mozz]

Fender lacquer potted pickups, I've dipped them in poly.

[Helmholtz]

Fender lacquer potted pickups

AFAIK, Fender did that in a period after ca. 1968. But it seems that those PUs showed increased (later) failures.

[mozz]

Job security, he said it was a emergency.

[Chuck H]

AFAIK, Fender did that in a period after ca. 1968. But it seems that those PUs showed increased (later) failures.

How do you retain all these details about vintage specifics!?! Between this and your tech chops you've been a real asset to the forum

[Chuck H]

Fender lacquer potted pickups, I've dipped them in poly.

I didn't know that. But I have to wonder if the magnet wire insulation wasn't different from what's used today. Lacquer thinner is pretty hot (fast, aromatic, strong) stuff. I'd be more worried about lacquer than I would CA glue actually.

The thing about thin catalyzed products is that you can't just let them sit there until you think they've penetrated enough. You're on the clock. Wait too long and you get a pickup inside a plastic brick Something I did once was to use a brake bleed pump (the little hand vacuum pump they sell at the auto parts store) siliconed into a hole in a mayonnaise jar lid. I put the catalyzed varnish (cabinet finish from a job I did actually) into the jar with the pickup, screwed the lid on and started squeezing the pump. You could watch the air evacuate the pickup in tiny bubbles. The action was very obviously accelerated with increased vacuum.

Even then I noticed the catalyzed varnish smell on that guitar for almost a year. If you leave a can of this catalyzed "finish" product unused it doesn't really completely harden in thicker applications for a long time. So there must be some evaporation aspect as well. But that guitar worked great without squealies until the day I sold it.