Here I go again :-).
The previous issue has been solved by an electrical engineer (don't ask about it 'cause I'm totally not in this stuff :-), only know one lamp has been changed + other replacement work). However it cost me around 70 euros to fix and the guy said that these amps (he repairs a lot of them) are not well built, in fact he said that I can expect other similar problems mostly because of the not-so-well heat dispersion, he just said: "hmmmm, I don't know" (like see you again :-(...)
Well after using it for some time, today I plug my guitar in and power up the amp and there is no sound, I put it in heavy metal mode (IV) and only if I turn the 2 volume knobs all the way up you can hear a very tiny sound, in fact you can hear what you play but only like you'd hear it on some headphones put on a desk in front of you :-). Anyone?
P.S. I tried different cables and checke the tube protection fuse...