The power LED on my HP Pavilion is permanently blinking, even when on mains. It also battles to 'awake' from Standby mode, just powering up without restoring. It also does this when I try and power up without mains.
I seem to recall an esoteric procedure to do this and that while pressing this or that, but it eludes me. Kudos to the person that can diagnose the problem and or remind me of the procedure.