Boden wrote:
E Z Peaces wrote:
Jeff Wisnia wrote:

The Daring Dufas wrote:



I had a friend some years ago who ran the communications
division of the local power company. This was back when
they had HF radios for communications and the techs actually
had to know something about electronics. They would get
electronic interference complaints which were often traced
to doorbell transformers. It was a very common problem and
one that many people don't even think of today.

TDD



Sorry, but I have a hard time believing that.

If it was "a very common problem", can you offer a cite proving that
a 60 hz transformer and 10-50 feet of unshielded wire with 24 vac on
it can cause interference at radio frequencies?

Wouldn't you expect that if that story was true those big pole pig
transformers and all that higher voltage wiring running on the poles
on nearly every street would have caused the radios to melt? G

Jeff


According to the FCC Interference Handbook, defective doorbell
transformers are often a source of interference to TVs and other
household electronics. It may be a neighbor's transformer. I think
it happens when part of the core comes loose and vibrates.

If the Guberment says so it must be so. I just don't believe it.

Several electric utilities say so. It can also come from microarcs in
transformers on poles. When they get a complaint, they check poles with
an ultrasound detector to pick up noise from an arc.

When a doorbell transformer fails, I imagine it's usually an open
primary. When it first opens, I imagine the vibration of the
transformer could keep the break arcing indefinitely.