EH Scott Radio Enthusiasts

The Fine Things are Always Hand Made

Borrowed photo from Todd as a pictorial. Thanks Todd. I’ve had this set rebuilt and enjoying the broadcast and phono output for some time. Unfortunately a recent startup was accompanied with HUM, increasing with volume advancement. I’ve tried tube replacement to no avail, where would you start looking ?

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Dave - Well, since the hum increases with the volume control, it is probably being introduced before the volume control. That means the Wunderlich detector, and IF and RF tubes are suspect. A very likely source is a tube, slight filament to cathode leakage, etc. If you have a known good 58, try subbing it for each 58 in the set. Same for the 57. A less likely possibility would be the 56 oscillator. If tube substitution doesn't identify/resolve it, the next most likely would be a leaky capacitor. Try the tube substitution and let us know. I'll study the schematic more to see if there are some capacitors that may be likely candidates.

Kent

Thanks for the advice Kent. The set has been recapped, I’ll check back inside after the tube swap. When rebuilt, the 55 with strapped cathode to pin, was in place. Following that I acquired a Wunderlich, which performed gloriously, Perhaps this tube has shorted ? I love the 45 sound in this set. Anyway, thought maybe a resistor but will eliminate other things first.

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