TriggerFinger

I understand from this that it does not SHUT OFF anymore... is this correct?

I do not think it is the RTC battery. If you have cracked the holder (if you can send up an image of this the better) may be you can glue that part back. When everything is fine, then put back the RTC battery.

About removing the heatsink.. if you mean you have removed the heatsink assembly (which includes the fan) from the CPU, make sure you have applied (reapplied) the thermal compound. This is NEEDED for better heat transfer from CPU to heatsink.

Do the above first. If you still get a blank screen, make sure you have seated ALL CABLES well in their sockets. Do them again if you have any doubts. If symptoms persists hook it up to an external monitor.