[ARC5] Transformer Hum

[Robert Eleazer]

I had a transformer for some lights fail at home so I started going though a pile of unknown transformers to see if one would do the job.  A nice big hefty one had two black wires and three red wires; two of the red wires had stripes. I decided that the back wires, with a DC resistance of about 45 ohms, were the primary and the red ones a center tapped secondary.

I hooked up my Variac and found that the secondary voltage came right on up, topping out at 194V with 120V on the primary - but just before it maxed out, the transformer started humming.

Would y'all take the humming as an indication the transformer voltage is too high?  In any case I was looking for one with a 12VAC output, so it won't do anyway.

Thanks,

Wayne