What is the fourth antenna lead that connects to the wi-fi card?

HI there. Thanks very much for your reply. I'm still confused though: I just tested the camera using Photo Booth and it's working fine, despite the fourth lead being broken / disconnected. I've just ordered a new antenna assembly, but that only has three connectors on it, whereas this fourth connector is an independent lead. All advertised replacements say 'ISight/Wi-Fi/Bluetooth Antenna assembly' but none of them appear to include this lead. The teardown description doesn't mention it either. All it says is 'remove the four antenna cables'.

Sounds like you ordered the wrong part. Is the cable connector broken or the board?

The board is fine. I damaged the connectors while replacing the optical drive a few days ago - it's necessary to remove the Airport card before removing the optical drive. I'm pretty sure I ordered the right part - I checked it against the model mumber - A1286 - and that it was a fit for a mid 2012 15" Unibody Macbook Pro. http://www.ebay.co.uk/itm/121718165508?_... As I said, the fourth connector appears to originate from a mount on the casing of the Mac that is separate from the other three connectors.