[Lucien Nunes]

Those are the two triode anode loads, so being open-circuit would stop the amp working completely. You have previously had sound so they must have been working then, even if out of tolerance. Due to their value and position it's more or less impossible for them to have been damaged by a fault elsewhere, and they can't both be from a bad batch of parts as they are different values. So that is distinctly odd and while not impossible if I came across that scenario I would suspect my own measurements to be in error e.g. from locking the range on the meter too low to measure them.

Some notes:

There is what looks like a dry joint on C8 at the V2A end. This will not completely stop the unit working if open, but if the dry joint includes the adjacent end of V2A's anode load (the 180k that's not numbered in the circuit diagram) then that would be as much of a showstopper as an O/C resistor.

The diagram appears to have V1B and V2B labelled the wrong way round. Looking at the PCB, V2A's anode drives its own pentode not V1's, and vice versa for the cathode.

The feedback resistor R11 has been replaced with the wrong value. The pic in post #1 shows it to have been 15k which matches the circuit diagram, but a 33k part has since been fitted. This won't stop the unit working.

What is that resistor on the underside of the board? It was there in the first pic but doesn't seem to have a purpose as all the necessary parts are present topside. It looks like 1M, and while I can't see its connections my best guess is that it is in parallel with R8. Is it?

The speaker lead connections to the tags topside, currently have the black lead to signal and the blue to ground. That might not be a problem if the black lead isn't grounded anywhere else, and indeed it might be correct. But if the black lead is grounded, the output will be shorted and no sound will be the result.

Next post will be about taking voltage measurements. It's time to bite the bullet.