Author Topic: Beta Lead - loud hum with no signal  (Read 22 times)

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Offline porcupine

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Beta Lead - loud hum with no signal
« on: July 14, 2018, 03:30:33 pm »
I recapped my Beta Lead and am now having some problems with it. After putting it back together I plugged into channel A. It sounded great for a few seconds and then there was a loud thump/pop sound. The channel LED went out and the amp stopped passing guitar signal, now just putting out a loud hum (which can't be controlled by any of the knobs). I shut the amp off immediately and opened it back up. Everything looked ok, nothing burnt and the fuses weren't blown, so I tried again.

Channel A worked great, and I played through it for a few minutes with no problem. Channel B worked but had a lot less gain at the exact same EQ/drive settings. I plugged into the Both input and I got the loud pop/hum again, no LEDs lighting up, and no guitar signal passing. Went back to the individual channels and I'm getting the same result. Any clues what could be wrong?

Offline loudthud

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Re: Beta Lead - loud hum with no signal
« Reply #1 on: July 14, 2018, 08:22:11 pm »
There is a -15V source on the power amp board. Make sure it is steady and has good connections to the preamp board. The channel LEDs run off of the -15V supply.