Well I will be looking forward to that. Can't wait to have this amp usable againI had one of these come across my bench this week, and I think I've found a fix for this problem. TLDR: disconnect the mute relay circuits from the DSP and use the standby switch to manually operate the mute circuit. This is a fully reversible mod, internally and externally, should you wish to undo it.
An explanation in finer detail:
Based on the lack of progress in this thread, I think the cause is firmware related, not hardware.
The DSP daughterboard controls both channel switching and tone/eq logic. However, the designers had a problem with the switching behavior during power on/off cycling, resulting in fun things like the high gain channel switching on at whatever volume it's set to (possibly 11) and then amplifying whatever pops and squeals this circuit makes as the amp turns on or off. Very fun, will blow your ears out.
The DSP engages a muting relay during power up and power down so your don't hear this.
What I think is happening is a programming bug where the DSP randomly locks up in the muted state. This can be fixed by power cycling the amp, but that's no good if you are playing a gig.
Disconnecting the mute relays from the DSP solves this, but reason for the mute circuit still exists. Connecting the standby switch to the mute circuit solves this: engage the standby switch before powering on and off the amp, like a normal standby.
The removal of the standby switch's original function does no harm to the amp. There's no good reason for them and leaving the standby engaged for long periods can be harmful to tubes. This new mute circuit is probably a better design, ironically.
Next post will include photos/ directions.
Glad I could shed some light on this absolute lemon of an amplifier. Please just avoid DSP amps, they aren't worth the trouble!