Ok, more follow up on the amp. I have replaced the 6U8A’s with a set of Sylvania 6GH8A’s, not matched but from a set of 5 tubes. I did measure voltages last night with the following results
V3/4
1 (255V) 295.3/299.6V DC
2 (55V) 0/0V DC?
3 (32V) 43.6/37.3V DC
4/5 (6.3AC) 3.7/2.6V AC, 4.6/1.6V AC...