Onkyo TX-SV 727 PROTECT mode

disconnect speakers turn up to 60 and see if cuts out if it does not cut out check your speakers

there is an internal shorting inside the amp that puts the amp in protect mode also check if the amp comes on after disconnecting the speakers

Hello, I am sorry about your issue. I f the receiver does not stay on with nothing connected it would need to be serviced. Thank you, Onkyo USA

There's a fre service manual here, you need to join tte site (free)

Onkyo TX SV727 Manual AV Control Receiver HiFi Engine

Just check your speaker cabling again. Make sure that all of them are seated properly, none is touching each other or the body of receiver. Rewire if necessary..
Are you using banana plugs for connecting speaker or just directly. Some times even a little tiny wire touching the receiver could trigger the protect mode. Be careful, since protect mode is sometimes not fast enough and it could blown a few trasistors in the power circuit.

Otherwise, do your bose speakers play out load on other systems?

Hold the VCR/DVR button in and press the ON/OFF Standby button. The display should briefly read CLEAR and then the unit switches off. If that clears protect mode, you'll need to redo the Audyssey and configuration setup as these will have been cleared by the reset.

HI check your speaker cables are not touching, also make sure "b" speakers are not on and that all your speakers are 4ohm or higher as this will cause the amp to shut down if they are to low an impedeance,The amp is protecting itself when it shuts down.

hope this helps.
CABLE GUY.

The problem here is that the output amplifier section has a problem. This is detected internally and the system shuts down in a "protect" mode. The output section really only kicks in when you attempt to bring up the volume. Another possibility is a problem in the "front end" where DC current is being passed to the amp section. Without takeing measurements, it is difficult to determine the exact cause. This should be a relatively stright-forward repair for a service shop and should cost about $20-$40 in parts plus the local labor charge.
Dan

Hold video1 and press speakers A button, it will say "clear" If the message protect appears again, then its service time.

i believe protect mode is because you have the wrong impedence speakers, they are too low (4 ohm? 6 ohm?) it chols work with 8 ohm speakers