Hey guys, i would like a bit of help. I have been running an older Yamaha receiver, the RX-V657 with no problems till now. It goes into protection mode after 1-2 seconds, but i can boot it up in diagnostic mode and see what's up.
So, long story short, first message seen when i boot it up is "tmp 249". The value keeps changing, from boot to boot though. Going into "Protection History" the last few values were 280, 347, 239 and 249.

Going into THM section i keep seeing the 200 value being recorded, sometimes more, and on one occasion jumping wildly from 100 to almost 350.

In diagnostic mode testing the audio (stereo) everything sounds fine. I am thinking it could be the temperature sensor being faulty? I am saying that because everything is running cool from what i can see.

If anyone can help it would be greatly appreciated.

https://drive.google.com/open?id=0B7PMFGkC1FmKSWlfZjJJT0xXdWM

 

The service manual might be helpful?

 

Thanks, i have it already though. The image i posted is cropped from it. Unfortunately the manual is a bit cryptic, at least for my understanding.

 

Not sure if it helps much, but the temperature IC is shown and described on page 44. You can buy cooling spray for testing electronics. It might be worth trying it on that part, after you find it and look it over. I'd also check the wiring through the connectors shown there.