Problem with my Diezel Herbert

Here is my problem with my 7 year old Herbert and I have no clue how to solve it:

From one day to another the amp has less power/ is quiter.
Yet I have checked and changed all the cables, tried another cabinet and changed the power tubes. Nothing solved the problem.

Any hints? May I have to change the preamp tubes?

if power tubes didn't fix it, change V1 preamp tube and maybe the PI. 99% of amp problems are tube related. and, if you have been playing it for 7 years with the same tubes, there's a chance they are your culprit.

steve_k":1qsoihe8 said:

if power tubes didn't fix it, change V1 preamp tube and maybe the PI. 99% of amp problems are tube related. and, if you have been playing it for 7 years with the same tubes, there's a chance they are your culprit.

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+1

Bad preamp tube

Thank you guys for your quick response. Preamp tubes are ordered and should arrive tomorrow. I will tell you how it worked.