Newbie with WAD 300b PSE monoblock hum

[sonic fiend]

Hi All,

Newbie with WAD 300b PSE monoblock hum. Really like these units and would like to use them more often, otherwise they may have to be sold to someone who has the time. I have looked through the previous message boards and found this to be useful but a hit and miss affair with not too many success stories. I do have some knowledge in electronics/repair and have had valve equipment for many years, i have also built my own diy amplifiers and the like with various levels of success and disaster.
I Bought the PSE monoblocks a few years ago, already used and they always had hum (same on both). I put a new set of valves in but nothing changed and actually got worse so put them away as i didn't have the time to look into it or any more££.
I got them out again a few weeks ago, blew off the dust had a look inside, The kit looks like a standard build and has been made well with good solder joints etc. I found some wiring that had come away from their original position. With the amp on so i could hear the change as I pushed the wiring back into position which helped a lot but still have a small amount of hum. Checked all valves on a tester and the power supply caps with ESR and capacitance meters and all good.
Any advice would be greatly appreciated and or possible upgrade with better components/circuit from the original.

Thanks in advance