[morzh]

David

Be methodical about it, don't do the cavalry charge thing.
1. Have you checked ALL your tubes? If not, do not proceed untill you do. Or buy know good tubes if you don't have a tester and replace all those with possible exception of audio output and maybe the rectifier as it seems like you do have voltages and such.
2. Try to pass a buzz through the schematic - touch grid caps of tubes involved and see if there is a reaction - buzz, or whatever - you should hear t in the audio. Be careful, fo not touch wrong stuff and while touching, make sure you yourself are not grounded. Or use a long metal object with an insulating handle if this feels more comfortable - screwdriver, soldering iron etc.
3. Provided your chassis does not smoke while being powered, measure all voltages according to the voltage chart. Compare, note all large discrepancies.

Then come back.