Hi,
I have a Chinese amp (yaqin ms-20l) that has recently developed a slight 120 Hz hum in the right channel. What would be the likely source of the noise?
I have a Chinese amp (yaqin ms-20l) that has recently developed a slight 120 Hz hum in the right channel. What would be the likely source of the noise?
Hum remains if I remove the preamp tubes, so I guess that narrows it to the power amp side of the circuit? Bias is fine as well.
Possibly shift in bias of the output tubes. This causes the PS ripple rejection to go down and you get more hum.
How did you check the bias?
Otherwise, it could be a bad output tube. Swap them between the two channels.
How did you check the bias?
Otherwise, it could be a bad output tube. Swap them between the two channels.
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