I've had my Sony STR-DE415 for about 10 years without a problem--recently it developed one. After turning it on, the display flashes "protect" and I get no sound. I no longer have the manual, so I'm not sure what this means or how to fix it. I've checked all the wiring and it appears to be in order--speaker cables are properly connect at both ends, as is the stereo cable from my CD player (also a Sony). Anyone know what's up? Thanks.
Disconnect everything from the receiver. Unplug it from the AC outlet for an hour. Plug it back in and try switching it on before you reconnect anything. If it still has this problem when you power it back up, you probably need a new receiver. Most likely the large scale microprocessor that controls most of the functions of the receiver has gone out. It's not worth repairing this on a ten year old receiver as the cost of the repair will exceed what you paid for the receiver. Buy something with new stuff on it.
'Protect' is activated (1) when an amp overheats or (2) a cross connection happens. If there was a cross connection some processors may have been gone, in which case you may take it to an authorized sony service center. Just check the repair estimate, if its what you'd like, go for a repair, else, you know!
If it was a simpel case of overheating, doing as Van above mentioned would fix the problem.