My AV receiver went into 'protection mode' (or just blinks its standby light and won't turn on). What now?

Protection mode means the AVR caught a short, or thinks it did, and locked itself to survive. The circuit is doing its job. Your job is to find the short instead of fighting it.

Before assuming the worst, one test that settles most cases. Disconnect ALL speaker wires from the back of the AVR. Unplug it from the mains for ten minutes so the protection circuit fully resets. Then power it on with nothing connected: no speakers, ideally no HDMI either.

Starts clean and stays on? The AVR is fine, and the fault is in your wiring. Classically one loose strand of bare wire touching the next terminal, or a strand bridging positive and negative on the same terminal, or a cable pinched behind the rack until the insulation gave up. Re-terminate every run neatly: strip cleanly, twist tight, no stray whiskers. Banana plugs make the mistake nearly impossible, which is why we fit them on every installation. Then reconnect one speaker pair at a time, powering on between each, until the culprit trips it. Sometimes the culprit is not the wire but the speaker itself, so if one pair keeps tripping the AVR with fresh terminations, swap that speaker onto a different channel to isolate speaker from AVR.

Trips even with no speakers connected? That is an internal fault: an output stage, the power supply, or a failed component that the protection circuit is correctly refusing to run. Stop power-cycling it. Every retry is another surge through a part that is already unhappy. Go through authorised service, mention protection mode with no load, and let them read the fault.

Two things not to do: do not bypass or "reset" protection by any method a forum suggests, and do not assume a blinking standby light is a software glitch. Send us a photo of the speaker terminals and the model, and we can often spot the stray strand from here.