[Elecraft] K3 Transformer Hum

[David Inger]

I was also noticing transformer hum.  I checked the mounting hardware and
found that the transformer was secure.  I plug my amp into a 20-amp nominal
120-v circuit.  When the transformer continued to hum, I checked the voltage
at the wall receptacle.  The voltage would, intermittantly dip to less than
105-v and lower.  It was under this low voltage excursions that the
transformer hum occurred.  It my case, it turned out the culprit was a
faulty circuit breaker at the service panel.  Replacing the breaker solved
the problem.  I would recommend checking the input voltage when you hear the
hum.
 
73 de K6SBA
David in Santa Barbara, CA