[TenTec] Fw: Loud Hum w/Paragon I & 961

[Dr. Gerald N. Johnson, electrical engineer]

You might try lowering the line voltage to the power supply. Hum is a
sign of the core being run to saturation (cheap design short on core
area and copper). It should get very much quieter with only a small
reduction in line voltage from either a variac or a bucking transformer.
You can lower the line voltage until the power supply regulators loose
regulation on current peaks (key down CW) and then raise it a hair. Many
utilities tend to run line voltage higher than 117 so that the 10%
change from no load to full load that can come from two transformer
drops after last regulating the sub transmission voltage still will keep
a minimum voltage as generally required by state utility board
regulations. Running lower line voltage into the supply will let the
supply operate cooler and more efficiently.

73, Jerry, K0CQ