It had a damaged 30 pin display connector (torn off by previous owner) on the logic board & also some minor damage to the 30 pin ribbon cable.

I bought a replacement connector and ribbon cable from eBay, just to be sure it would connect properly.

Numbers listed on eBay for the ribbon cable:
Part Number: 593-1006 922-9132
MPN: Y593-1006 922-9132

I reassembled the machine, but it would not boot at all. No startup sound, no beeps, nothing. However it does boot with the display disconnected.

I have ordered an adapter, Mini DisplayPort (Thunderbolt) to VGA/HDMI/DVI, to see if will run with an external display, as a workaround.

But I would much rather fix it properly, so it runs with the built in display. Can anyone shed some light on this?