Troubleshooting a dead Onkyo TX-SV727 Receiver - Pwr Supply Suspect

Now that you have tried a few things to see if you can see something wrong, I would suggest you take it to someone who understands something about electronics. Based upon your text above, I get the feeling you would not be able to replace the faulty component even if it were identified for you. This is NOT meant to be a slam, but advice that might save you some money in the long run.

Seconded. This is almost certainly an output stage failure, and in a DC coupled amp such as this, may well be cascade in nature. These are potentially tricky for the best of us, and a set of schematics, and the ability to understand them in detail, is certainly required to even begin to tackle this sort of problem. Depending on where exactly in the circuit the fuse that's blowing is located, there is a slim possibility that it could still be something simple in the power supply such as the bridge reccy, but if you do not have experience of detailed fault location to component level, I would agree with the good advice given by Ken, and consider taking it to a reputable repair shop.

Arfa

Problem with the amplifier is usually suspect if no blown fuses and you get a Protect warning. Unless you have explicit experience in repairing consumer audio electronics I strongly recommend you take the unit to a qualified repair facility.