Unfortunately there's little information to go on. Firstly is this an IP system (NVR) or analogue HD system (DVR). It's easy to identify...How did you 'unplug' the camera? If it's an NVR/IP system you've unplugged a plastic RJ45 network connector, if it's a DVR/Analogue HD system you removed a coaxial cable by twisting and retracting the round BNC connector. My guess is you have a DVR.
If it's an analogue HD system connected to a DVR there are several possibilities:
- Poor termination. The BNC is poorly fitted at one or both ends of the cable. Moisture may have got to the connector at the camera end. When this happens it creeps between the outer sheath and braid screen of the coax, corroding it and massively increasing its resistance until it fails completely. Here's an example of a poorly fitted BNC causing that issue (an electrician had fitted the connectors incorrectly using pliers and as usual muggins here is the one who has to tell the customer they were robbed by an amateur):
View attachment 11147
- Suspect power supply. Less likely as this would usually show as noise in the image that gets worse on a night when the infra red LEDs increase load on the supply.
- Faulty camera. I've seen many failures of Hikvision analogue cameras over the last 10 years or so but only 1 or 2 IP cameras.
As you've indicated that you replaced the camera and the fault returned on that channel, it would indicate that the camera is not at fault. Start by swapping the connections of the channel at fault with another in the back of the DVR. If the 'No Video' fault moves to the new channel, it's likely to be a cable/termination fault. If the 'No Video' still occurs on the same channel (different camera connected) it could be an issue with the DVR itself.