German made (1963) stereo in console cabinet. Chassis has had a complete recap with those small yellow capacitors and all filter caps have been replaced. Four of those capacitors are .022s in the volume control circuit. C95, C100, C83, C78. The best I could do is replace them with outside foil shielded caps, and wrapped metallic duct tape around them, grounding the foil tape. That significantly reduced the hum, but it's still there when volume is turned up. Not very noticeable on AM, FM, but when you go to phono, since it has a lower output, turning up the volume control the hum gets louder. (There's no hum with the volume control turned down). It's there on all the functions, but more noticeable on phono since I have to turn up the volume higher as I had to replace the cartridge with a standard ceramic type. Hum is being picked up by EMF either within the unit or from EMF interference in the air. I have tried moving wires around to reduce it, (which helps), but can not completely eliminate it. Other than enclosing the whole unit in a metal box, (which is impracticable) does any one have any other suggestions. I really can't go with a different cartridge as the original is unavailable. The one I have in there (which was a bear to mount) was recommended by Gary at VM.
Here is a link to the schematic. I feel I have done my best, but wondering if anyone has any more suggestions.
https://app.box.com/s/3th2xptdo035qmqtw2mz
11-20-2016, 04:58 PM
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