Could be any of the 5 output amps, the sensing circuits or the CPU IC. You'll need a schematic to troubleshoot it. All 5 amps have a transistor Q401-Q405 2SA1162 (Protect) near them which monitor current flow to that output amp IC. These 5 all connect together to Q406 near IC321 on the main board.

Q406 should have +5V on the collector. That goes to pin 2 of IC321, out pin 3 of IC 321, then out connector D to Digital board, thru R112 to pin 53 of IC101 (CPU IC) on the digital board.

If you have +5V on pin 53, the CPU is bad. Part # 6-800-673-01 IC101 MB90553ABPF-G-209-BND. You won't, so you have to find out where the problem is.

"Davy H" wrote in message ups.com...
I have a SONY a home Cinema system (STR KSL5) which after about 2 mins
shuts down with the word PROTECT in the display screen. I have checked
all the speaker outputs and they are fine, no shorts. I have removed
all the speakers and the same problem occurs. The fan works so doesn't
seem to be an overheating problem. This PROTECT fault occurs even when
the volume is turned right down therefore not driving the amp. Anyone
have any ideas what might cause this fault? and how to rectify it?

Thanks

Davy H