Rectifier used in HMV 2022 Record Player.

[Old Sparky]

I have now completed the rewiring of the 2022's amplifier, and it is working, but a bit prone to instabillity. Having followed the original layout as closely as possible, I'm wondering whether the absense of centre spigot from the valveholde might be the cause of this as it would affect the capacitance of the valve & holder to ground. Despite using the original contact coole rectifier, the HT is higher than specified at 270v, admittedly measured with a DMM, so perhaps this is the cause. Any opinions/ suggestions as to the cause of this problem. At the moment the amp. & speaker are on my bench rather than mounted back in the R/player's cabinet