Mesa Boogie Maverick repair

[leydenjar]

I have a Maverick that only puts out very low volume UNLESS a jumper cable is plugged into the fx send jack. When plugged into this jack the amp's LEAD channel works great, sound great, shows no isuues, however the rhythm channel still barely outputs any volume at all. It doesn't matter whether the fx send/return jacks are connected or the patch cord is just left dangling from the send jack.

All voltages on the tubes test ok or at least very close to the schematic.

I can see two of the relays actuate when the lead/rhythm because someone has exposed the inside of the relays.

The fx mix potentiometer works fine/tests ok.

Thanks for any help in advance. Pic and schematic attached.

[soundguruman]

sounds like a bad optocoupler.

[g1]

Sounds like you are dealing with 2 separate issues. As far as the FX loop, is it wired up like the schematic shows? The send jack should have 3 wires. Sounds like the switch contact is wired to ground. It should be wired to the wiper of the FX mix pot.
There is an LDR for muting in the rhthym channel, you could try disconnecting the leg that is connected to V4 pin 2 to see if that is a problem.