Working on an Admiral 20X12

[old_coot88]

The B+ is 'waay too high, suggesting there's insufficient load to pull it down to spec. Likely the H.output stage is not conducting.
There's B+ on both sides of the fuse, right?
Since The damper is in series in the B+ pathway to the H.out stage, an open damper would cause your problem. Have you subbed the damper?

If so, with the set off, check for continuity from the fuse to pin 5 (plate) of the damper. Should be about 11 ohms.
Then check from pin 3 (cathode) of the damper to the plate of the H.out tube. Should be around 165 ohms.