Hello Gary, Thanks for the suggestion, which I believe has proven to be conclusive.
I hooked my Variac to the primary and slowly increased the secondary voltage. The caps were disconnect from the rectifiers, so the transformer was "all by itself". At about 700 volts, the voltage started to jump just a bit. At maybe 750 v, the secondary emitted a puff of smoke with an accompanying hiss. I think it is clear that the transformer is shot. Time to call Peter Dahl! Again, thanks for your input. 73 de Dave Gary Blau wrote: > If you have an audio oscillator and ac voltmeter handy, inject 60Hz at > 1V into the primary and measure the secondary. That should help you see > if there's a ratio/shorted turns problem. > > Next would be to slowly bring the xfmr up to full input voltage with a > variac, with a light secondary load. If it survives the voltage test > then the trouble is likely in the load somewhere (rectifier, etc.). > > g > > Dave Aabye wrote: > > > > Good morning all, > > > > I need some advice. > > > > Earlier today my Viking 500 tripped off with the familiar odor that we > > have all come to dread. I only lost HV. > > > > After I got the cover off the PS-Mod unit, I was surprised to see > > nothing unusual. Then I started sniffing, and that led me to the HV end > > of the plate transformer. I removed the end cover and again saw nothing > > unusual....only the odor, which by then was beginning to dissipate. > > > > Resistance measurements lead me to think that some windings may be > > shorted. One side to center tap reads 110 ohms. The other reads 95. > > The manual says 100 on either side. The HV secondary shows infinite > > resistance to ground, but that is with no juice applied. > > > > What I'm wondering is whether the 15 ohm difference is conclusive. If > > not, what other tests might I make without risking further damage? > > > > Thanks in advance for any advice, > > > > Dave, W4QCU > > Oak Ridge, TN > > _______________________________________________ > AMRadio mailing list > [email protected] > http://mailman.qth.net/mailman/listinfo/amradio
