1/ reboot you ps3 with the rear on/off button
2/ press the on/off button until you listen 3 bip ( 1 after 2 bip )
3/ the ps3 will restart
now ,if you see the recovery menu ,you can reinstall a ofw (put a lv2diag.self on a usbstick and do the downgrade method )
if you see a ylod > go buy an infectus
You could know if ur ps3 is really die just by seeing the led activity of ur usb stick .
If you see the usb stick is flashing on the boot ,you could restore it ;if you see nothing > Rip ps3