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"Protect" is an indicator that the is a short in the speaker outputs somewhere. It is either a shorted wire, pinched, or frayed wire or a blown speaker, speaker terminal touching the chassis or in the worst case a shorted output transistor in the deck itself.
Try initially disconnecting all of the speakers (being careful not to let the wires touch each other ), and power the unit on again. If protect is gone, then connect the speaker one at a time until the unit goes into protect again. This speaker will be the one you need to trace down the problem with.
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