Protect flashes in display

SOURCE: Denon AVR-810 going into PROTECTION mode

It sounds like there is a problem with the differential circuit. The bias I am not sure about, as every unit is different. You should get the service manual to be sure or call Denon and see if they can give you an idea. Good Luck

SOURCE: Sony amp str-db940 - protection

Somewhere in your speaker wiring, you have a shorted wire. This short can be as simple as a single strand of wire touching the other terminal on one of the speakers.

With a bright flashlight, look carefully at the back of the receiver and then the speakers for any loose strands.

SOURCE: when you turn on the avr 600 the display says "protect"

The Control IC broken

SOURCE: STR-DE475 receiver flashes "PROTECT" when turned on

Protection is usually a sign of overheating or something is wrong at the power amplifier's output.

Theory: Protection is a delay and sometimes an internal test to allow the electronics to stabilize during power up before they are allowed to interact with the speakers. The most common cause of it remaining ON is that a speaker cable pair is shorted. Some isolation is required...

1. Turn the Power OFF.
2. Disconnect each set of the speaker wires that are directly attached to the receiver. Mark them so you remember where each one went. pay special attention to which conductor is on "+" or "POS" and which is on "-", "COM" or "Ground". You may elect to disconnect them one pair at a time if your sytem is complex and you don't want to lose track of where things were.

Turn the Power ON. Is the "Protect" indication gone from the display?
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If YES, you have a shorted speaker wire or speaker. To isolate the specific cause:

1. Turn the Power OFF.
2. Attach ONE speaker wire pair at a time and test it by turning the Receiver ON. When the "Protect" light returns you have isolated at least one of the cause(s). Disconnect the defective speaker cable and continue isolation of all speaker cables. Visually examine the cable at both ends for frayed wires that could touch each other or contact metal on the receiver or other objects.

To isolate further within the cable/speaker pair - disconnect the speaker end of the cable on the failing path. Try another cable that you know works, or at least one that doesn't cause Protection to stay on.

If you're electrically savvy and have a Digital Volt/Ohm Meter you can troubleshoot the short(s) with it.
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If NO, there is probably an internal problem.

Is it solid or does it come on after the Receiver has been ON awhile.
It could be overheating.
Is the unit hot to the touch?
Is there a cooling device (fan)?
Is it stopped or clogged with dust?
Is there adequate ventilation around the unit for air to flow?
Clean any ventilation slots on the top and bottom of the unit.
Avoid stacking components that produce heat under an amplifier or receiver. Their heat rises. Also keep them away from other heat sources like like home heating vents and radiators.

Problem solid and NOT related to the speakers or heat: internal malfunction.

Let me know.

SOURCE: Sony STR K840P, protect mode is flashing,no

This is a classic problem. One of your speakers is miss wired and or your speaker wires positive and negitive leads are touching. Check all connections from the back of the reciever to the back of the speakers to make sure your positive and negatives are correct and that none of the wiring is crossed or touching one another.