Hello, I have a PS3 that starts with a green light and then flashes red with three beeps, after that it shuts down. I've determined it's a component failure after testing the HDD and psu for faults, both work fine. There aren't any visible signs of failure either.
That indication is normally overheating - but if it's doing it immediately on power up then it's probably cracked solder joints on the chips. This is extremely common on the CECHA/CECHB units - to the point where it's really a question of when rather than if. It's also hard to say which chip is causing it - the RSX seems to be the most common followed by the CPU, but it really can be anything.
Typical YLOD. Not much you can do other than reball, which is something most people don't have the equipment for.