Harman Kardon 930 troubleshooting

Hello John,
Thanks for posting on the Forum. The way I try and trouble shoot a piece of electronics is to first isolate the power supply from all of the sections of the device that it is connected to. In a receiver there are, probably, power supply connections to the tuner, pre-amp and power supply sections. Usually they will have separate wires going from the power supply to these individual circuits. If so, then disconnect these wires, making a drawing of what color wire goes where. Now the power supply is isolated from the loads. Instead of a fuse in the main AC line substitute an AC current meter and connect the receiver to a Variac (hopefully you'll have one of these). So you'll be able to slowly increase the incoming AC Voltage and watch what is happening with the current. There shouldn't be too much of a current flow as the AC Voltage is slowly increased. If you can reach a full 110 Volts with less than .5 Ampere flowing through the meter the power supply should be fine. Then you can check what the Voltages are that are supposed to go to the various sections of the receiver. Look on the schematic and note what the DC supply Voltages are supposed to be and see if this is close to what you're seeing. You might want to measure the DC resistance of each of the sections of the receiver, the tuner, pre-amp and output stage. Try and look at the schematic for each of these sections and determine what it should be. For example if the tuner section has a resistor in series with the incoming power supply Voltage, see if the readings you get for that corresponding connection seem in line with what you would expect. Be suspicious of a reading that shows 0 Ohms. That would indicate that when the power supply is reconnected it would be developing a Voltage across a short. Not a good sign.
I hope this is helpful information.
Regards, Ken