1 of 4 CCTV Cameras Won't Work

I have a HomeGuard 4 camera DVR CCTV system, and yesterday evening I noticed one of the cameras was out.

After some fiddling around today I'm confident it isn't the cable, as the camera situated next to it worked perfectly when I swapped the cables.

However, here's where things get strange. The camera that was out yesterday works, but only if I plug in 3 cables into the DVR box, not all 4. It uses BNC RCA cable with a separate 12 V supply and splitter.

So I'm wondering if it's a problem with the DVR box, rather than one or more cameras. But the camera that was out yesterday that is now working has awful picture quality compared to the others. It's all faded and distorted.

I try swapping round all the cables to different channels/ports on the DVR box and it makes no difference.

Any advice would be appreciated.

Thanks.

Hello. Have you tried connecting each camera by itself to the separate 12 V supply? If they each seem to work OK or equally badly, you may want to consider a new separate 12 V supply.