Modern CCTV (closed circuit television) cameras are very reliable, but sometimes they can fail. The most common cause of camera failure is due to the wiring. The wiring of a CCTV camera is fairly simple; the camera requires a positive voltage, a negative voltage or ground and a 75 ohm cable to deliver the signal to the monitor.
Check your monitor, recorder and camera for the proper settings.
Check the voltage at the power supply. You should have approximately 12 volts DC or 24 volts AC depending on the type and age of the camera (check the label on the power supply for the correct supply voltage). Inspect the connectors and wires at each step for corrosion, loose or frayed wires and bad connectors. Replace any defective connectors. If you do not have voltage at the power supply, you have a bad power supply.
Check the voltage at the camera for the correct power supply voltage. If you do not have the correct voltage at the camera, you have a bad cable or wire coming from the power supply.
Disconnect the RG-59 cable at the camera and insure you have a 1 volt peak-to-peak signal coming from the camera. This will be a voltage of approximately .707 volts AC if you have a standard RMS (root mean square) voltmeter. If you do not have the correct voltage coming from the camera, you have a bad camera or connector. Reconnect the connector.
Disconnect the RG-59 connector coming from the camera to your monitor or video recorder. Make sure you have a 1 volt peak-to-peak (approximately .707 AC volts for a RMS meter) signal coming from the camera to the recorder. If you do not have the correct voltage coming from the camera, you have a bad cable or connector. Reconnect the connector.