Guitar tube amp output hum - The Valve Combo 2/50

[Niketouille]

Hi guys,
Today I have that great amp on my bench. I can't find schematic or service manual and the only info I got is bias value.
Output stage induce hum in the audio output. On the scope it looks the same as the ac residue on the HV.
Hv seems to be only filtered and not regulated. Output stage is classic EL34 PP and some resistors had burned in the past.
I swapped output tube, set bias and it does not change anything.
Anyone got an idea, a starting point, a schematic, a solution maybe...
Cheers,
G.

 

[ruffrecords]

Check/replace HT smoothing caps. Check interstage caps for leakage.

Cheers

Ian

 

[Niketouille]

OK thanks, I will look into it.
Cheers,
G.