Onkyo Won't Turn On Main Relay Failure Confirmed Replacement

Glad to hear you got it working and this fixed the problem.

I have seen this a couple of times. One word of caution on simply replacing the relay with a 12V version is that on some models (I haven't checked all), Onkyo places a 150ohm 1/2W resistor in series with the relay. The function of this resistor is to reduce the voltage/current going to that relay but you won't see the voltage drop until the ground is applied from the transistor they use to turn on the relay.

I recently repaired an NR717 that not only had a blown relay but had also fried this transistor (Q9101) and the diode that is in this circuit (D9100). My immediate reaction was to change out the relay but almost immediately, the diode and transistor blew again. What I found was that the 150ohm resistor had degraded to about 147 ohms and was allowing too much voltage/current to be applied to these components. The "fix" was to replace the resistor with a brand new one (measured at 152 ohms) and then change out the transistor/diode pair again. I also replaced the relay with the original spec'd 9V part. The Receiver has now been working perfectly for over a month.

I suspect that these resistors are the root cause of the issues with blown relays and would encourage anyone doing this repair to check the 1/2 watt resistor to make sure it is equal to (or a higher value than) it's spec.