Testing an output transformer...

[Bob M.]

I'm building an amp with 2x 6V6s, Class AB. I found what looks to be an old/used output transfomer appropriate for a Deluxe Reverb-type power amp in my box of junk. It looks to be 3rd party/aftermarket. Can't remember where it came from.

What's bothering me is when measuring the ohmage of the primary, the two sides seem a little far apart from one another. From the red center tap to the blue outside winding lead measures 212 ohms and from the red center tap to the brown outside winding lead is 184 ohms. So this is a difference of about 28 ohms between the two sides. I seem to recall that I'd see a difference of about 10 or 11 ohms in a new/good Deluxe Reverb transformer. Is this anything to be concerned about? Any opinions?

I know it works, at least ok, because I had this transformer in another amp in the not too distant past.

Thanks in adv,

Bob M.

[Gtr_tech]

It should be fine. You'll normally have a slight mismatch from each end to the CT because of the way its wound. Nothing to worry about.....

[Enzo]

Fancier transformers are wound with two pieces of wire, starting from the center tap, and they will be pretty close. SImpler transformers use a single winding. Stop at half the turns, connect a tap, then continue on. SO the one side is wrapped around the other essentially, so the wires are longer for the same number of turns. Longer wire, higher resistance.

[Bob M.]

Thanks for your replies. As I recalled, the amp that was using this output transformer in question wasn't anything to write home (or to the forum) about so I decided to replace it anyway. I then came across a box of brand new Heyboer transformers that I (almost) forgot about. So I skirted this issue. I guess the acid test is to put this tranny into a good sounding, working amp and see if it continues to be good sounding, or as good sounding. I guess I'll get around to that little test sometime. I was concerned because it was a greater number than I'm used to seeing in OTs.