Need Help with 60 Cycle Hum in Tremolo Circuit

Chuck Martin · From: Clifton, Virginia

Here's a clearer description of the problem:

I have a Music Man HD130 Reverb head that has a 60 cycle hum that is heard when the footswitch is connected and in the "off" position and the intensity control set above zero. The hum pulses at whatever the "speed" control is set for. The hum volume is only affected by the master volume control and at lower settings its not very noticible. When the pedal is in the "on" position the hum is gone, same as when the footswitch is not connected. I notice that if I move my hand close to the footswith the hum volume increases. In fact, at higher master volume settings I hear a local radio station through the speaker even with the channel volume on zero. Any of you techs ever run across anything like this?

Chuck Martin · From: Clifton, Virginia

I may have answered my own question. This problem may just be a characteristic of the amp design. The hum problem was significantly reduced when I tried a fender reverb footswitch that has tin braid around the cable. My conclusion with the 60 cycle hum and radio pickup is that the music man footswitch is acting like an antenna. I will probably just buy some shielded cable to fix this problem.

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