Written by Jim Shank 8/2/05
There should be two major troubleshooting points for CCTV, the camera’s themselves and the central terminating location (CTL) in which the video signal is captured and the power is supplied (if power is not supplied mid-run or directly at the camera location). Troubleshooting will be started at the CTL and then move to each individual camera. It helps to have a baseline camera that is working in order to capture normal readings for comparison. Remember that CCTV cabling should be as follows
| RG-59/RG-6 | UTP with Baluns | Fiber Optic | |
| Run Length | < 250 ft. | 250 – 3000 ft. | > 3000 ft. |
Tools Needed
- Digital Volt Meter (DVM)
- Electrical Tape
Optional Tools
- BNC or F-type connector and small piece of coax
- 9V battery
1) Determine and mark which power line corresponds to each camera.
2) Take the baseline readings from the good camera:
a) At the CTL, check the voltage where the DC adapter is connected to the line for the power run and verify correct voltage and amperage according to the power supply. You may need to disconnect the DC adapter from the power run line to read voltage. VOLTS _________________ AMPS _________________
b) At the CTL, disconnect the camera power source, typically a DC adapter, from the power run line and read the resistance to the camera: OHMS ____________
c) At the CTL, disconnect the video terminator and check the resistance from the middle pin and the outer shield towards the camera: OHMS ______________
d) At the good camera, disconnect power and video and check the resistance towards the camera (this will check the camera itself, skip if you have a monitor to test). Read the resistance at the power connector: OHMS ______
Video connector: OHMS______
3) At the CTL, for each camera power line, perform the same tests and compare.
| Camera | Power Volts | Power Amps | Power Line Resistance | Video Line Resistance |
4) If the power supply reads nothing or incorrectly once disconnected from the run-line, replace the power supply. If the resistance is infinite, there is a break in the power line (unless the working camera read infinite resistance).
5) Disconnect the video terminator (F-Type, BNC, etc) from the device (Computer, VCR, Monitor, etc) and read the resistance towards the camera, once again if this is infinite, you have a break in the coax and you will need to check the connectors and finally replace the coax if you can’t repair it at the connector.
6) At the CTL, reconnect the power supply to the power run line for each camera.
7) From each camera, disconnect the power line from the camera and check the volts and amps on the power line towards the CTL, they should be the same as the original CTL-side readings.
8) Creating a loopback tester:
a) Using the terminator and the short piece of coax, terminate one end of the coax with the BNC or F-Type connector.
b) On the other end, strip back about 3 inches of insulation so that the core wire is exposed and a good amount of shielding is exposed
c) Cut the shielding, lengthwise (do not cut it away from the rest of the shielding completely) and spin it together.
d) Touch the shielding to the core and secure (you can just wrap it, use electrical tape or soldier but in the voltage test, this will need to be disconnected)
9) Connect the loopback connector at the camera end towards the CTL.
10) At the CTL, use the DVM to check for continuity back to the camera, if no continuity, the cable is broken or the connector is not fully connected and the run will need to be replaced or the connector repaired.
11) Creating a cable integrity tester (CIT): This will rule out in-line shorts
a) Disconnect the loopback core wire and shielding
b) Connect the shielding to the negative side of the 9v and the core to the positive side of the 9v using electrical tape or soldiering.
12) Testing: YOU MUST disconnect the camera and video terminator from both ends of the line or the equipment could be damaged.
a) From the camera side, connect the CIT towards the CTL.
b) Using the DVM, check the voltage at the CTL end of the video run, it should be approximately 9v. If not, there is an integrity problem somewhere in the line where the core is touching the shielding. The run should be replaced or the terminator/connector reconnected.
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