Harold sez: ". . .More likely due to corrosion . . ."
That's about it - but - the joint has to be open in the first place for
corrosion to occur. A good solder joint won't corrode to the extent of
failure; a bad solder joint is already an "open" invitation for corrosion.
Corroded joints act, electrically, as diodes. A piece of loose "tie-wrap"
(tower jargon for radiator hose clamp) on a tower can form a diodes capable
of supporting destructive intermodulation interference to receivers on the
tower. That's probably what got into Harold's microphone. Motorola's
famous engineer, Russ Larson, once found corrosion inside a large neon sign
to be the cause of extreme intermod on a building antenna site in Kansas
City. Russ proved the point by pouring some motor oil down into the sign.
This type of corrosion-diode formed interference is recorded ad infinitum in
the history of crowded radio communications sites.

Bob Swinney


"Harold and Susan Vordos" wrote in message
...

"Chuck Sherwood" wrote in message
...
Perhaps, but solder work-hardens ... a LOT. If the joint is subject to
even slight vibration or flexure, the solder-only joint will eventually
fail.

I have personally fixed a few "cold" joints in old TVs just by
reheating the solder joint. I suspect the failed connection was
related to mechanical stress.

.. I've experienced such a phenomenon on a
microphone input, which had started acting as a detector and sending a
radio
station to the amplifier. "Honest, Mr. Madsen, I didn't have a radio on
while I was running the sound system."

I was vindicated when I found the corroded connection.

Harold