Hi Hamish

do you mean the CIB with the RGBHV BNC connectors on the front? If so, this is just a straight through from the VGA to the BNC, so the fault would lie somewhere else unless the cable was damaged.

If you mean the DV1 interface, this had VGA in and then the signal was sent through a couple of DA's and then to the VGA and BNC connectors. If its this interface, check the power etc to the DA's

regards

Nev.