This video shows quick and easy FIRST step of troubleshooting receiver or amplifier with no power. In this case the only failure was a blown main fuse. So there was nothing to "repair" other than to open the cover and replace the fuse - ALWAYS FOR THE SAME RATED VALUE!!!
I connected the Onkyo receiver to a Kill-A-Watt type of device which allows for a quick and easy test of power consumption. Very low power consumed - below 2 Watts - in both ON and OFF positions indicated that the main transformer was not getting connected at all.
It was the main 4 Amp fuse that failed, and no other problems were discovered at this time.
If the correct fuse blew up again, then the next step would be to look at failed output transistors, and so on. However, never replace fuses with greater Amps value than the original!!!