Hallicrafters rebuild update.

[Tom Albrecht]

Phil, if your coil was known to be bad beforehand, and now appears to be permanently fixed, that would be good news indeed.

I have to admit I would be somewhat surprised if this approach offers more than a temporary fix. If moisture is in fact the problem, there is no polymer coating of any kind that can keep it out for more than a few days or weeks. Polymeric coatings are generally quite permeable to water.

Ability to insulate is mainly a separate issue, so there is no particular reason why a product geared toward good insulation would be good at keeping water out of a coil and preventing the overall lossiness in the structure that results from that. I suspect this insulating coating is a nice choice for reducing tendency for corona, etc.

I've done the clean, bake, and coat approach on a Hallicrafters 505 coil, and found the improvement was only temporary.

However, what did work was to mount a cooling fan inside the HV cage on that same Halllicrafters. Now it works fine.

Previously, the HV would start out OK and then go low after 10-15 minutes. It seemed the combination of old, moist coil and a little heat build up resulted in the fade.

And as I recently reported on ARF, I successfully replaced a Philco coil with a surplus Motorola coil, and am having good success with that.

So far have not had to resort to an alternate HV module.