The power switch is in the upper left corner of the front panel. If you do some disassembly you can access the power switch circuit board. Use your continuity checker to confirm that the power switch works properly.

Unlike older electronics that I am familiar with, AC power does not pass through this power switch. Instead, pressing the Power button sends a signal to a chip that turns on the receiver.

The power switch circuit board is a little tricky to get to. As an alternative, if you happen to have the IR remote control that goes with the Sony Receiver, just press the power button on the remote. If the unit powers up by remote but not the front panel switch, then the front panel power switch must be bad.

If the unit fails to power up with the remote, then the failure could be due to the remote, or it could be something else.