Hi John! You mean that your wonderful xyl lets you use her oven! 68F here today!..73..Jeff..W0XV ----- Original Message ----- From: "John Leer" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, February 12, 2003 6:24 PM Subject: Re: [AMRadio] Re: 500 Transformer
> Regarding drying transformers etc. I have been drying transformers and > chokes for quite a few years. I have used both electric and gas ovens > with no apparent difference in results. I store my spare transformers in > an unheated outbuilding and temperatures here in Wisconsin run from -20F > to +100 so condensation can be a problem in many different devices. I > first check the resistance from winding to core with a small hand held > megger which applies about 1000 volts. I find many transformers and > chokes will have an indication of leakage to ground after a year or so > in storage. After baking for 4 hours or so at 200+ degrees and allowing > to cool, the megger will indicate infinite resistance winding to core. I > have found a something strange, to wit, if the measurement is taken soon > after removal from the oven , the megger will still indicate a leakage > resistance. Upon cooling the resistance will usually be infinite. The > transformers with tar type potting seem to be the worst offenders at > absorbing moisture. I assume this is due to cracking of the tar. John > K9XH > > Donald Chester wrote: > > > > Be careful about using a gas-fired oven to dry out the transformers. Water > > is a by-product of gas combustion, and the air will carry plenty of water > > vapour. Better to use an electric stove oven. > > > > If you are in no hurry, bring the transformer into a dry, heated room and > > store it there over the winter season. By the time you start cutting off > > the heat in the spring, the transformer should be well dried out. It is > > more effective to let the moisture gradually evaporate from the guts of the > > transformer, just as it gradually condensed there when the transformer was > > in a moist environment, and there will be less likelihood of abnormally hot > > temperature causing deterioration of the insulation. > > > > Don K4KYV > > > > _________________________________________________________________ > > Add photos to your messages with MSN 8. Get 2 months FREE*. > > http://join.msn.com/?page=features/featuredemail > > > > _______________________________________________ > > AMRadio mailing list > > [email protected] > > http://mailman.qth.net/mailman/listinfo/amradio > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio >
