Is this a 12 volt DC stereo, or a 110 volt AC stereo? If it is 110 Volts Ac, he needs to check the circuit breakers - The fuses are for the 12 volt DC circuits. A digital Voltmeter (DVM) is a basic tool needed for troubleshooting in our electrical world. With the meter you can determine where voltage is present, and where it is lost, to track down the source of power loss.