You are totaly right, with my text I gave to understand wrong thing (I'm sorry, my english is bad). The true story is:
I have forgot to disconnect the amplifier from the mains before attempting anything (very stupid), and a short circuit ocurred in the 120 / 240V selector, in the back of the radio (maybe it touched the metal frame).
I dont think the amplifier was exposed to overload, because my home's mains is only 120V, the minimum setting on the selector.
The "power" switch between the transformer and the PCB was in OFF position, but maybe the current made their way trough the frame, not the switch.
Well, is not only "it doesn't work", it does
, but instead of music it only generates hum when a wire is connected to phono in, even if the other side of the wire is without load. And with load, for example my computer, the hum goes much more louder.
Even if they seem undamaged, I'll follow your tip and check the diodes and condenser from the +42 volts line that enters into the pcb. I'm worried about the mains wich could touch the metal frame (the ground of the amplifier) and the damage is beyond repair.
Thank you very much by your help, Hero999. Any other suggestion will be extremely apreciated.