JOLIDA Issue

Very possible you could have had a bad tube from the start. Call your dealer (or Jolida if bought used) and let them know what's going on.
Whenever dealing with tube products, the tubes are always first suspect when there is a problem.

Russian tubes are junk, Chinese not much better.
Anybody who thinks they sound good must of never heard an amp with good America, British, German, Hungarian or French tubes.

I sure hope it is just a bad tube and not something with the "guts" of the amp. I purchased it from EBay, the outer shell is in mint condition and the seller did a heck of a job with the packing, it was well taken care of.

Thanks for the replies, I'll report back when I install the replacement tube.

RIGGED

"I was able to turn two pots several revolutions without reaching the stop point."
Normal for multiturn bias trim pot, which the newer Jolida units has. Bias should have been checked after shipping before power up.
The multiturn pots make for more precise setting unlike the older single turn ones.

When replacing the tube make sure and turn the pot down several revolutions, it's a 12 or 13-multiturn pot.

Tubes can fade away or die spectacularly, both of which has happened in my 502p with no issues issuing from the amp. That's tubes for ya. A note on Shubert's post...I love my NOS UK origin Mullard 12AT7s, but I've had really good luck with Russian Gold Lion 12AX7s and KT120s, 150s, various new Tung Sol and EH stuff, Mullard reproductions (in my class A 18 watt guitar amp), JJs, etc., and I think you can learn a lot more from fooling around with tubes than paying much attention to fools around tubes.