I have a sony str-de335 fm stereo receiver and

if you disconnected everything and it still goes into protect, the most likely there is a damaged amp channel that will need to be repaired.

It depends how much you are ready to pay for the repair? I would ask for an estimate from a repair shop.

Please see the link below for an explanation of protect mode. After that, please post here any additional questions that you have. Specific to your model, you can expect a parts cost in the $40-$60 range for the repair.

Dan

Link: http://www.fixya.com/support/r5390728-protector_means

PROTECT display indicates that receiver got serious problem in output amplifier section and protection mode is activated to avoid further damage.
Output amplifier section should be tested by qualified technician to find out and replace defective part(s) to solve this issue. Local repair shop will do this job as it is not user level repair.
Thanks.

Turn it OFF. Look for shorted speaker wires or shorted speakers.

None found? Disconnect all speaker wires and try to turn it on.

Turns on ok? One of the speakers/cable pairs is shorted. Check them again.

No good? It's dead. take it to a tech.


http://www.retrevo.com/support/Sony-STR-DE335-Receivers-manual/id/387bh942/t/2/

Your manual is here : http://www.docs.sony.com/release/STRDE335.PDF

it is over heating

This generally means you've got a short somewhere, and the received is trying to protect itself.

My suggestion is to disconnect all of your speakers at both ends, and reconnect them.

Most times this happens because a speaker wire is lose, and the positive and negative connections are touching each other, causing it to short out.

The audio amplifier IC are fried and need to be replaced

In all likelyhood, one or more output transistors have failed. Please confirm your model as STR-DE335 and I'll post the probable parts that need to be checked.

Dan