Apply oil to preserve HV transformer insulation?

Discussion in '"Boat Anchor" & Classic Equipment' started by K7GLD, Nov 28, 2018.

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  1. K7GLD

    K7GLD Ham Member QRZ Page

    I picked up a neat, pristine old Gonset GSB 101 amplifier, and am curious as to any method to maintain or preserve the condition of the OEM HV transformer. I've had some very nice oil-filled HV transformers in the past - which were sometimes referred to as "self-healing" in regards to windings damage that would otherwise ruin an open-winding transformer. Not sure how accurate that might be, but oil-immersed transformers primarily used for added cooling effect, are nothing new - but could there be any "preservative benefit" realized by carefully applying light weight oil as thoroughly as possible to the exposed windings portion of the HV transformer such as used in many older and irreplaceable transformers? If so, any particular type of oil that might be best? General thought is that such an application might disperse internally thru capillary action, to wick pretty well inside the windings and insulation - any thoughts, or just a waste of time with potentially unconsidered nasty side effects?
  2. N2EY

    N2EY Premium Subscriber QRZ Page

    I would NOT do it!

    Oil cooled transformers are designed for the oil used with them. The air-cooled transformer in that amplifier isn't.

    Plus when it gets warm the oil will go all over the place.

    73 de Jim, N2EY
    WA7PRC and N6UH like this.
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    I agree.

    Maybe transformer lacquer would be better to use.
  4. W1BR

    W1BR Ham Member QRZ Page

    Vacuum impregnation of the lacquer might work. Some rewinders offer that service.
  5. N2EY

    N2EY Premium Subscriber QRZ Page

    Maybe. BUT - I wouldn't, because I don't know how the new stuff would interact with the old.
  6. K7GLD

    K7GLD Ham Member QRZ Page

    WELL, I suspected early on it was likely a losing proposition. The few old transformers I've disassembled in earlier years - some had failed, others not - pretty much all showed dried out and brittle flaking insulation wrapping. In those cases, all I wanted was the wire they contained. It's pretty obvious to me, that in otherwise properly used transformers, age and heat deteriorates transformer inner insulation and sometimes the enamel wire coating as well, leading to eventual shorts and failure. I had only mused that there might be a workable, externally applied treatment to somewhat restore effectiveness of inner insulation that inevitably is lost thru years of heat/cooling cycles that break down inner materials. The "mess" of excessive oil runoff would be a minor issue, and easily controlled - IF such a treatment was otherwise helpful in extending the life and performance of an irreplaceable transformer. Then, there's the potential that chemicals that soften insulation, might also soften and damage the protecting wire enamel as well :(

    BUT, I reluctantly agree, it's likely an exercise in futility - just thought I'd ask... Thanks...
    Last edited: Nov 28, 2018
  7. KK6IYM

    KK6IYM Ham Member QRZ Page

    Modern lacquer is mostly acetone solvent based--air quality rules--but even old lacquer had a fairly active solvent--so that it dried quickly. Varnish however has a very benign solvent--paint thinner. Paint thinner, mineral spirits, kerosene, even VM&P naphtha are not very active and don't dissolve much besides wax and graphite--stuff like that. I would suggest you use a varnish as a way to protect the wiring inside old transformers. It penetrates well and dries very slowly which again helps with penetration. It is fairly water proof--especially the modern urethane varnishes. I would not recommend any water-based or "new-type green" paint thinner-based varnish or urethane.

  8. WB2GCR

    WB2GCR Ham Member QRZ Page

    Varnish, impregnated with varnish. Not lacquer.

    Modern winding shops use a polymer, not varnish usually.

    You can do the job urself with either glyptal or spar varnish.
    Pull a vacuum in a pressure cooker, that pulls the air out of the internals.
    You need to modify the old pressure cooker. Don't "borrow" the XYLs!

    Julius Futterman, of OTL amplifier fame did the job on his kitchen stove,
    with heat! :D

    Then you'd want to dry it thoroughly before using. End bells would be off, of course.
    Would it keep it from breaking down? Maybe.

    You could take the end bells off and have a look-see at the guts, some
    transformers had the windings impregnated.
    KA0HCP likes this.
  9. K6BSU

    K6BSU Ham Member QRZ Page

    I have fixed "buzzing" power transformers by using poly varnish poured into a coffee can. The transformer was soaked for a day, then dried out for several days. The process was repeated once more.

    I did not see any advantage using a vacuum to remove any air bubbles. There is enough penetration just by soaking. A few air bubbles remaining are trapped forever in the dried varnish.
  10. WB2GCR

    WB2GCR Ham Member QRZ Page

    The goal of insulation and eliminating buzzing are not quite the same.
    For insulation, one would want to not have voids. Afaik.

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