solidifying toroid core position and windings?

This is the correct stuff to use.

If your toroidal inductors are wound that loose, you'll have damage in shipping, mostly from the enamel coating falling off from vibration. Some kind of conformal coating will help.

Before selecting any coating, lookup the loss tangent values and see if it will get hot due to RF losses. If you're not sure, coat a PCB with the coating, let it dry, and bake it in a microwave oven. If it tends to crumble, burn, melt, or otherwise self destruct, find something with less loss. 1kW at 2.4GHz is a rather brutal test for a coating that only needs to work up to 30MHz, but is quick and easy. If it survives at 2.4GHz, it will work at 30MHz.

If the BP filter is designed using high Q inductors and mechanical vibration detunes these inductors, your design is faulty and you will have other problems, such as multiple problems caused by water. I used to design marine radios and quickly learned that high-impedances, high-Q tuned circuits, and high voltages were really bad ideas in a marine environment. So, we designed most everything using low impedances, low-Q tuned circuits, and low voltages. The result was that the radio worked nicely when wet and did not require any kind of coating. Such coatings are a mess to apply and handle. Rework is either difficult or impossible.

Here's an example from about 1980. This is the Intech Inc Mariner

3600 150w PEP SSB HF marine radio: The large board full of toroidal inductors are the TX/RX LP (low pass) filters. We didn't use or need BP (band pass) filters. Notice the lack of any conformal coating. I will admit that we did use some wax to keep the synthesizer VCO from becoming microphonic. It was also one of the few circuits that were sensitive to moisture.

Good luck.

This is exactly what I ended up doing, dissolving foam in acetone. It didn't mix the greatest as I should probably have used a different solvent, like ethyl acetate, but it got the job done. And I still have plenty left over in a sealed jar.

Thanks for the info. I should have mentioned that this was for a receiver and will never be used for a transmitter. I ended up making the poly glue myself using white foam dissolved in acetone. Works fine. Took about 8 hours to fully dry. Very sold result and non-conductive.

On Sun, 13 Feb 2022 07:55:55 -0500, Jake T snipped-for-privacy@steak.com wrote: (chomp)

You may have goofed. If you are using enamel, lacquer or shellac insulated copper "magnet" wire for winding your coils, the acetone solvent will dissolve the insulation. I suspect the reason you observed a "solid result" is because the "melting" insulation has now glued itself to the insulation on adjacent turns. That's pretty good if you can keep it from moving, but since dissolving the insulation also makes it thinner, I suspect that any movement will cause intermittent shorted turns.

Hint: Check a chemical resistance chart for whatever you're using for insulated wire before using any solvents: "Enameled Wire Insulation Characteristics"

Before wave soldering machines switched from using chlorinated hydrocarbon solvents to clean off solder flux (about 1974), to aqueous (water) based cleaning solutions, we used to use vapor degreasers loaded with trichlorethylene solvent to clean PCB (printed circuit boards), which included the boards full of PE (plain enamel) magnet wire wound torroidal inductors (as shown in the M3600 photos I previously linked). We had to use a special insulated magnet wire AND keep the temperature very low in the vapor degreaser, in order to not soften the insulation. We also had to learn not to touch the coils until the PCB was dry and at room temperature. Polyurethane based insulations were better but still required some care.

Good luck.

Ah, good points here! I wondered about using acetone from the start, should have checked this further. Well, pretty hard to test the toroids in circuit now as there are caps across them, so I placed an identically wound spare in acetone for a few hours just to see what occurs.

I see the MSDS for the actual Q Dope is a mix of the poly and MEK. I was going to go with that formula at first, but I only had acetone on hand and I can't seem to find MEK locally. There's something called MEK substitute and the MSDS for that seems to indicate that it is ethyl acetate. I can get the substitute, but then the question becomes whether or not the ethyl acetate would dissolve the enamel. I used to use pure ethyl acetate in the past to euthanize insects as entomology used to be one of my hobbies. So it, like acetone, can be quite potent.

Well, the good news is that the enamel wire wound toroid I placed in acetone for 8 hours showed no signs of breaking down. I feel confident that the filter coatings are ok. That's about how long they took to dry in the circuit. However, the points you made here I won't forget soon in case I run into a questionable future wire.