[Kenwood] TS-830S Problem - Hum

[Dr. Gerald N. Johnson, electrical engineer]

Generally I'd associate 120Hz with an opening electrolytic capacitor in
then power supply. Could be high voltage or low voltage. With no hum on
receive, its more likely the high voltage power supply. If its 120 Hz
hum. If its 60 Hz hum (and sinewave, not the sawtooth from the power
supply) its most likely coming from heater to cathode leakage in a tube.

Aluminum electrolytics have a limited lifetime that is shortened to
about two years of not being operated. After two years of setting they
need reforming and often that's not successful. So they operate with
considerable series resistance and there's ripple from the power supply.
The only cure is replacement.

73, Jerry, K0CQ

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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.