I've tried everything in the process of elimination as far as to detaching all the speakers, checking the speaker terminal jacks for possible short circuit using multimeter and even removing the top casing eliminating the connection for each circuit boards while powering the unit. It seems the one that causes the problem is the amplifier circuit board, tried disconnecting the ribbon cable between the amplifier board and the main board, powered it up and no more protection error was displayed. Now I need to go deeper in to component level check such as the driver transistors etc., I had already checked all the electrolytic capacitors, mylar capacitors, the exhaust fan, the inductors and they all seems to be fine, what I have not checked so far in the amplifier board is the power-amp IC's, I don't know I still need an expert advise please help.