Electronics > Mechanical & Automation Engineering

covering up solderable elements for vacuum varnishing?

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I am wondering what a good way to 'resist' coat transformer solder points before a vacuum varnishing dip (mg chemicals red insulating varnish).

I just made sure its plugged with solder and then painstakinly use many q-tips damp with paint stripper to clean up the solder terminals.. but its a real pain in the ass.

I thought one of these might work
1) wax
2) loctite 'fun tack' (I see it dissolving and possibly contaminating the varnish)
3) self amalgamating tape (if its available in a very thin form that is easy to apply to fragile transformer solder areas

It seems to get under tape.

Does anyone have a known good solution before I attempt the next one ? It's going to be a while since I need to buy another container of varnish, maybe someone will come up with something by then.

I don't have any of those materials on hand to test it myself and I don't see myself needing them unless they work for this.

I wanted to dip, air dry, expose and bake. I hate dealing with the wet transformers, so they go right to the drying rack after I take em out of the varnish and then I leave because it totally smells like shit and I end up looking like I got war paint on whenever i work to clean em while their wet, very stressful

I have some experience with 3M 70 and I can confirm that seals, but I see 2 problems :
1. Vacuum: if its not perfectly applied, the varnish will get in.
2. Price; ~50USD/30ft roll sounds steep to me.
I think the best bet would bu to show a picture/drawing of the solder points.

they are like this

I have another varnishing job coming up so I need to make a decision.
So cut little square of the tape and apply to each terminal ?

If you have stand-out terminals similar to the pot(green line), even folded over Kapton tape should do the job; two layers each side, each pin individually wrapped.
In the case if you want to protect the rivets which holds the stand-out terminals(red line), the 3M 70 is better choice.
Both type of connection can be found on the transformers, that's why I present both options.

I tried the self amalgamating tape. I cut strips of it and pressed them over the wires with my fingers so they make a tight seal. I also wrapped it around some nuts.

Basically it was total fail, the tape that was like wrapped uber tight on the nuts kinda stayed on, but it came off all the tiny wires. The stuff in the varnish makes it loose its seal/integrity. There was still some bleed through on the nuts/standoffs. Its like not easy to do right. the geometry of these objects is shit.

If there was like a small bakalite board that stuck out alot with the terminals, like that potentiometer I figure maybe it could have worked. But this transformer had just fragile wires that were PCB soldered... so it won't work for that.

SO what you need to do is to get 2 q-tips, after its varnished and air dried but not baked, dab them in paint remover solvent, then wipe it off by grabbing the wire and pulling on it gently, and you can also put 1-q-tip behind the wire, and take the other q-tip and twirl it while pressed into the wire to get the partially cured varnish off.

These HP things only have like 3mm of protrusion for the solder points on top (for the mains, not the low voltage direct wire2pcb), and it came off there.

Most of these solderable elements are not just robust enough to properly wrap in self amalgamating tape. I can try kapton on the next one......... I got one more....... |O I am thinking candle wax though. Fucking pain in the ass.

The varnish was first dilluted with a little bit of ethyl acetate a few months ago when I was in a bind, then before use I shook it with the proper MG Chemicals thinner, which kind of smells like acetate, before use, and did a vacuum degas with pressure adjusted to prevent the varnish from boiling (adjusted the needle and vacuum flow valve to 24mmhg or so, I can keep a fairly stable pressure with the proper valves on the rotary vane pump), I use 1x needle for bleed at the pump intake, 1x needle for the vacuum chamber intake and a wider bore multi turn valve between the vacuum chamber and the vacuum hose, and I fit that with some 20um or something stainless filter block at the chamber intake, I can trim pressure nicely but the needle valve is a bit low flow so you need to adjust the choke valve, which limits flow quite a bit.. but it operates OK in the "getting rid of bubbles without boiling solvents range'.


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