• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

MC275 Hum Conundrum

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I replaced most of the caps in my MC275. Power up test revealed a loud hum. Making sure of my wiring I chanced to approach capacitors C1 and C12 with a pair of needle nose pliers - the hum got substantially louder perhaps 6 - 9 db or so. An aluminum framed magnifying glass also increased the hum. A plastic pen did not.

What do you think?

Thanks in advance and Happy Fourth.
 
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