Hi Tim,

This is not an HRM right? I know the amp is a bit different than the HRM, but I did a video including the problems I had. It might not actually tell you what your problem is, but you might get some pointers from the stuff I had videod at the time.

My problems revolved around basically the extra little boards (not the main boards). Nik talked about those extra boards being very picky about how much solder to use - too much and they form balls of solder which he said could distort the boards if overtightened and had caused trouble before. Funny thing was, that although my problem appeared to relate to one channel, it was actually there on everything - and when the output 'went off' it became VERY hard to find.

I checked all the connections on all those boards - in my case it did not make a difference, but Nik was very specific about that. All the same, I would check for too much solder, because he was so specific about that problem and the aggrevation it had caused before. Also slack off the non main boards from being too tight and see if the thing works.

Remember its not always wired wrong. In my build I did not have a single wire in the wrong place...

Nik also referred to bad dressing of cables - check that too.

My Power amp also worked perfectly - and I could even drive it with a pedal....  perfect - but the preamp was not.

Since, you have signal from the 'return' jack to speaker, don't waste your time on power tubes and the phase inverter  (v3 + V4 and V5) just yet.
So my suggestion would be to focus on the circuit from input jack to 'send' jack and nothing else.

I agree,...
it looks like you should focus on V1 wiring.
Can you post some photos?

BTW can you hear relays clicking when you flip that switch?

Did you try if PAB works or jazz setting perhaps?

Just to cover all bases.

Just a quick thought - Could it be a fault with the send/return jacks??
try connecting the two with a jack patch cable