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Mesa Boogie Nomad 100 amp, 2001?

Phantom channel change, randomly. Was with footswitch board only, they then used the rotary sw on the rear and now that is playing up. I'm assuming like the notorious Fender footswitch problem, but will it be drift of R values here as well, or ps/Vreg failing rather than the internal Vreg of the weird LM3914 bargraph driver use (no bargraph display) causing problems and just reflecting faultmode varying analogue Vs . What is the function of that 3914 if the relay switching points are determined by voltages,Rs and zeners

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N_Cook
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Looks as though the LM does decode/determine which ch relay is on. So monitor input V on p5 with different footswitch and rotary sw settings and then a muliturn pot instead, to see what voltage window does what. dot1 output for ch1 relay,dot3 for ch3 relay and ch2 must be absence of dot1 or dot2 signal. Hopefully +1.8V, -3V or LM Vref is moving around, to explain both footboard with all that TTL and rotary sw now causing the same problem. Also check whether 2 channels are ever on together

Reply to
N_Cook

Problem with the integrity of the grey ribbon IDC link between main and rear boards

Reply to
N_Cook

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