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Mesa Nomad had funny acting treble

9/16/2004 11:33 PM
Jack Collins	Mesa Nomad had funny acting treble I have a Mesa Nomad on my bench right now. It's the 55 watt version. 3 channels. On each channel the treble (and to a lesser degree the middle) controls are acting really wierd. As you turn up the treble from 0 all is well until it gets to about 6. Then there is a pronounced step and then as you continue to turn it up, it almost sounds like a wah pedal or something. As the treble is maxed out, the volume fades and treble is actually rolled off. The middle control is wierd in kind of the same way but not quite as strong. My guess is that the tone pots on each channel control the same tone stack through switching relays and that there is something wrong with the stack, the relays or ? Anyway, it must be something they all have in common. Anyone have a schematic for this thing that they wouldn'd mind sharing. Also,any tips on tracking down the problem will be appreciated. I haven't tried swapping any tubes, but I suppose that is worth trying.

9/16/2004 11:33 PM

Jack Collins

Mesa Nomad had funny acting treble

I have a Mesa Nomad on my bench right now. It's the 55 watt version. 3 channels. On each channel the treble (and to a lesser degree the middle) controls are acting really wierd.

As you turn up the treble from 0 all is well until it gets to about 6. Then there is a pronounced step and then as you continue to turn it up, it almost sounds like a wah pedal or something. As the treble is maxed out, the volume fades and treble is actually rolled off.

The middle control is wierd in kind of the same way but not quite as strong.

My guess is that the tone pots on each channel control the same tone stack through switching relays and that there is something wrong with the stack, the relays or ? Anyway, it must be something they all have in common.

Anyone have a schematic for this thing that they wouldn'd mind sharing. Also,any tips on tracking down the problem will be appreciated.

I haven't tried swapping any tubes, but I suppose that is worth trying.

Replies:

Dai Hirokawa IIRC, I think I've read something w... -- 9/17/2004 6:31 PM
Enzo Call Mesa and ask them about it.... -- 9/18/2004 12:44 AM
Don Symes Do the controls of different channe... -- 9/18/2004 7:47 AM
Brad I don't have the solution but I do ... -- 9/28/2004 5:23 PM