And I did it. Went to the studio and tested the amp. Same thing. Then I looked inside... And I founded the upper left speaker with the +ve broken and loose. That speaker was not working at all. The fast-on male conector happens to be broken. I managed to stick it and tested the amp. A completely different animal, oh my! much fuller and no hars and much proyecting sound than before. I don't know since when is broken, many gigs and movings from bar to studio, van, venue, van, studio, van, venue, studio and on and on... who knows how much time This night I have a full rehearsal with the complete band and this thursday we have a gig so will try how it works. I will weld that lead and double check the others before doing nothing else. Fender amps are quite thought. Nothing broken inside so far.