I have an S/200 that has a horrible hum that goes away if I remove the ground on the power cord. I am a technician by trade but I can’t say I am familiar with audio circuitry. I can read a schematic but that don’t mean I could troubleshoot this without some suggestions.
Unplug everything else in the room from the wall AC outlets, and just plug in the amp with speakers.
If possible, use shorting plugs in the amplifier inputs. Does it hum now?
If possible, use shorting plugs in the amplifier inputs. Does it hum now?
Last edited:
So I get the him when the amp is connected to the speakers (obviously) and the rca connections are made to the receiver. Both connected to the same electrical outlet. Happens in multiple homes. Problem does not happen with my other amp.
Sorry when you said receiver I thought you meant preamp. I don’t use any am/fm receiver. I have a Music Hall turn table. A Marantz CD changer, and a blue tooth adaptor. I get the hum with all of those disconnected.
Then that means there is a problem with your amplifier in rejecting earth currents and I would start at the power supply both the input to it and the output from it .
I am hampered by the fact I don't have a schematic which would show me the design but start checking for any mains input filters and power supply output filters then check any star earthing or even earth connections for a high resistance connection .
I have found what I think is the schematic --yes there is an input filter check C7+C8 and its earth point , nearly all Fet based circuitry as its liable to high impedance pickup check the input switching .
I am hampered by the fact I don't have a schematic which would show me the design but start checking for any mains input filters and power supply output filters then check any star earthing or even earth connections for a high resistance connection .
I have found what I think is the schematic --yes there is an input filter check C7+C8 and its earth point , nearly all Fet based circuitry as its liable to high impedance pickup check the input switching .
Last edited:
well I went through the re-capping process and cleaned an tightened everything while I had it open and the hum sems to have gone away. Must have been a loose ground. I did after a day of burning in those new caps my amp was still hot the next morning. I kind of doubt it hasn't cooled off yet so I may need to take a look at that power switch.