Swann camera not working

[the wall]

I have a NVR 7400 with NHD-818cam cameras the other day one was showing video loss then after 5 hours it came back on for a week then went off and not worked since, i have changed cables, ports and tried in another position and tried a reset still no life.
Are there any other camera that are compatible with this system.
I have a mate who is very good at circuit boards does anybody know what each wire carries i.e power, sound, video etc

 

[the wall]

Thanks for the info i will check this out.
I have the camera working now as said in the post my mate found the problem, to his surprise there is a circuit board in the ethernet connector on the camera and moisture had seeped in and corroded a connection.

 

[TonyR]

But you can also use Reolink cameras like an RLC-410 or RLC-420 etc which may cheaper. Reolink has been releasing new revisions under the same model numbers but I believe they are all compatible with a 7400.

FWIW, there are extensive posts in this forum that are negative for Reolink.