Originally Posted by bsanborn
If it was a bad connection, that is a bad connection problem. If it is a power rail issue, that is a power supply/delivery problem. Both of which would not require a new motherboard, therefore not motherboard problems.
I'm not talking about the black box which you plug into the mains power.
The Power Rail / PSU Line is part
of the DC/DC board which is part
of the Motherboard
A failure of the external PSU (the transformer unit) wouldn't cause what's described unless the battery was flat and even at that I'd expect the machine would switch off rather than parking the HD on and off (if that's what it's doing and it does sound a bit like it).
Additionally and to clarify the 'bad connection' theory, I'm talking specifically about the SATA connectors which are soldered directly to the... Wait for it... Motherboard.
It would seem that whatever it is might require some specialist attention, so it could be a warranty job?