Transformer doesn't pass audio until I slam it with signal

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wmtunate

Well-known member
Joined
Jun 7, 2006
Messages
300
Location
Detroit
I've got a pair of mil surplus Ferrodyne 600:600 transformers that I snagged off the 'bay a couple weeks ago.  One of them works fine.  The other passes audio, but only when I slam it with signal, somewhere in the neighborhood of +25dBm or so for a few seconds.  It's like suddenly unclogging a bathroom drain, and it will pass normal signal levels fine after that, but only for about a day or so and then I have to do it all over again.

Is this a common symptom with open windings?  When it's not working, I'm measuring an open circuit with the DMM.  After it starts working, DCR matches what I'm reading on the other (working) transformer.
 
That's what I figured.  Must be internal to the epoxy-potted case.  I've tried [over]heating the leads to reflow whatever is inside without any success.

I've got it in the freezer right now to see if I can force the winding to open up sooner.  That will at least tell me if it's heat-related.
 
Sounds exactly like the symptom of a broken winding or the solder connection to the leads inside the winding, if there are any.

.max
 
Hi wmtunate,

i don´t think it´s temperature-related.
Sounds like broken winding to me as ioaudio stated.
When a winding is broken (and not a solder-point you could be able to reach) it is finished because it all takes place on the inside of it-sorry... :'(
 
Given that it's sensitive to the signal level then that seems to imply a contact problem - oxidisation or dry joint.
I have something similar on an insert point (TRS switched socket) where a loud signal will make it work temporarily - although more like minutes than hours.
 
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