I fired up a more accurate tester and went through all the tubes. I was amazed to find 13/22 tubes are bad. Either failing on transconductance, gas or grid leak! Even both the 6AL5s are really dead - almost no emission. Typically, I find one or two bad and a few weak tubes.
All the crucial tubes are good though - some relatively new. Like the 6CD6 HOT, both paralleled 5U4s, 6W4 damper and 1B3 HV rectifier. I wonder if that was enough to produce some sort of image or sound and the owner kept running it into the ground ?