ok, thanks, so saying this in my language I replace the seethrough box with the one you gave me the link to?
btw the relay was recently refitted by a tech guy cause it was the reason for some crackling in the right channel and it really cured that. The amp overheated before the repair already. I don't know if it is still original factory relay, I will examine it.
This is what the tech guy wrote me:
I traced the fault to the protection relay contacts. I could bring the fault on and off at will by moving the relay. I took it off the board to inspect and the contacts did not show any significant wear although they were tarnished. I cleaned them and refitted it. There are a number of transistors on the same board that run hot and the soldered joints to these have suffered so I have remade these for good measure. Once reassembled all was well.