[BC] Humming Preamps

[Mike Holderfield]

If it is intermittent and in a multi-story building don't
forget the elevator service. I've heard it happen.
Every time they moved, a buzz & weird harmonic sound.

mike

Gary Peterson wrote:

> I've seen two situations where hum or buzz got into radio station audio
> equipment via the power line.  The first time, it was a water heater that
> was defective.  Every time the heating element came on, hum appeared in
> several pieces of audio gear.  Some were tube and some were solid-state.
> This was circa 1968.  It was located by flipping breakers in each panel in
> the building until the hum quit.  A replacement water heater solved that
> problem.  I guessed that there was leakage between the 240 VAC in the
> heating element to the plumbing and electrical ground.
> 
> At another site, circa 1985, a buzz appeared, from time to time, in the
> preamps on the Carousels in the automation system.  This was traced to some
> recently installed track lighting, with a SCR dimmer, in another office in
> the building.  All attempts at filtering out the noise, at the source,
> failed.  We finally bought them a Variac-type of dimmer.
> 
> If you can do it, start shutting down various circuits and see what happens.
> A couple of FRS handheld radios would come in handy.
> 
> Gary, K?CX