Is this happening in a regular pattern. If so please check from the mains power section.Check from the plug, the socket, use another outlet if possible to check. If the faultt recurrs, then you willneed to open the set when it trips off, check all the connectors, the main PCB for any signs of bad joints caused by dry soldering in heating sections. If so use a good iron to resolder these sections bbut attempt only if your familiar with these circuits. Next notice if there is any excessive heating when it is cutting off, if so reduce the treble and bass to confirm any transcient noise running the amp.Use another source to recheck if the noise is coming from the present one. I hope this helps. Good day