[Station X]

Time to try it in anger then.

I assume that the audio coupling capacitor connected to pin 2 of the EL84 has been changed?

When applying power be ready to switch off at the mains socket if anything untowards happens.

If you monitor the HT when powering up it should rise once the rectifier has warmed up, then fall as the other valves start drawing current.

If that's OK check that there's no, or very little, positive voltage on pin 2 of the EL84 measured wrt chassis.

If that's OK it's time to plug in a guitar and see if the amp works.