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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net
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