Carvin V3M relay issue

[glebert]

I've got a customer's Carvin V3M rev D mini tube head (though 50W with 4xEL84) on the bench. Symptom is very low and distorted sound. When I trace a signal through the amp on the clean channel (Ch 3 for whatever reason, thanks Carvin!) it looks great up to the K3.B relay, then it basically disappears. I have not dug too deep into it, and questioned if it was worth fixing, but customer wants to fix it even it it costs more than I would spend on it. Transistors for switching and driving the relay coils look like they are SMT so that might be a PITA, but they are in a open area of the board so rework is definitely feasible.

Anyone come across this sort of issue with this amp or similar?

TIA,
Greg

[Delta362]

I have not. However, I do have the unblocked schematic for the big brother V3 100W head, which uses the same preamp circuitry. Combine that with the 2nd sheet of the V3 blocked schematic to get the interface controls and you might be able to piece it together?

[Delta362]

Take a look at your V3M schematic in the lower left for the CH3 REL circuit. Does Channel 1 or 2 work ok? Those would be the NC contact on K3. Could be as simple as a bad K3 relay contact.

[glebert]

I haven't probed through the circuit with ch 1 and ch2 yet. Kind of a PITA to probe as the relay contacts are on the bottom side of the board and there aren't convenient components to probe on. I think spending a little more time on it will help, just thought I would ask the question. Seems like MEF needs a little more activity these days anyway.