1) Overheating- If you are playing a game and the PS3 suddenly turns off, you get the PS3 3 beeps and it flashes a red light, your PS3 has probably overheated. Leave it for about 20 minutes to cool off then place it in an open, well ventilated, space on a smooth, hard flat surface. Never use it on a carpet; they trap the heat and can block the ventilation vents. Also over time excessive heat can damage the internal components of the PS3.
2) CPU or GPU error- If you try to turn on the PS3 and it beeps 3 times and gives you a flashing red light then you may have a serious problem, the CPU or GPU may have been disconnected from the motherboard. Try the simple fix below; however if that dosen’t work, you may have to send your PS3 to Sony or see attached PS3 repair guide and fix the PS3 3 beeps yourself.
Simple Fix (PS3 Hard Reset):
A hard rest will change your PS3 settings back to the factory settings. To do this:
• Put the PS3 in standby mode
• Press and hold the power button on the console of 10 seconds until you hear 3 beeps