#16
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"Hum" pickup is often not hum but buzz ... 180 or 240 Hz and up, up, up.
This is often pickup from wires connected directly to the power transformer or direct to the line. If the filter capacitors are grounded will away from the transformer it may well be unfixable keeping the radio near original. I've fix it by completely redoing the power supply with 1N4007s and two modest electrolytics and two modest series resistors, right at the transformer, and letting the resultant somewhat filtered DC go around the radio to the tube rectifier and filter caps. |
#17
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Quote:
jr |
#18
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It depends on whether you want to use the rectifier as a dropping resistor.
This is unwise if you have unreliable heater-cathode rectifiers prone to shorts. |
#19
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#20
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Once, I bent up a piece of 3/8 copper tubing and threaded the leads from the power transformer to the rectifier tube inside the grounded tube... I will try the diode trick if I run into a stubborn hum problem again... thanks for posting!
jr |
Audiokarma |
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