Need Help -- Old CCTV System Interference Problem

[varack 0]

Hello All,

 

This is my first time posting and probably the only way I can figure this problem out. My company recently bought a new building and it has an existing CCTV system that was not hooked up.

 

However, I am experiencing some problems to actually getting it back up and running. There are 2 central power supplies a 12VDC and a 24VAC. The 24VAC run the longest runs of about 400 feet and to the outside cameras. The 12VDC are the shortest and are only interior cameras.

 

Problem: When one camera is powered on 2 other cameras also power on for some reason (the red positive are connected to the power supply on but the negative are disconnected). I cannot understand this for some reason. The cable that was run is Siamese 95% Copper Shielding RG59. When all cameras power on, numerous are unclear and staticy on the top left of the screen. Is this a ground loop problem? ALl BNC crimps are taped with electrical tape to prevent a ground loop on the steel framing.

 

I also was wondering is it true that the DC cameras use the shielding in the RG59 and the (-) Black wire are connected inside the camera itself?

 

I traced the wires back and fourth and they are not spliced anywhere or have any nails or anything through them.

 

Edit: Let me clarify it.

 

Line 1: Connected both + and - in Power suply

Line 2: only + connected

Line 3: Only + Connected.

 

When Line 1 is powered on, both Line 2 and 3 also power on with the - disconnected

[Soundy 1]

I also was wondering is it true that the DC cameras use the shielding in the RG59 and the (-) Black wire are connected inside the camera itself?

 

...

 

Line 1: Connected both + and - in Power suply

Line 2: only + connected

Line 3: Only + Connected.

 

When Line 1 is powered on, both Line 2 and 3 also power on with the - disconnected

 

This is exactly what's happening: because the power and video grounds are tied together inside the cameras, and the video grounds all tie together at the DVR, the other two cameras are getting a power ground via the one fully-connected camera. This COULD have something to do with your interference - does the noise go away when you properly ground all cameras to power?

[varack 0]

Thank You for the reply. No it actually gets worse. When i connect them all the problem gets worse. I tried all the possible solutions thinking it is a ground loop problem.

 

Here is what i have done so far.

 

Taped all BNC connectors to make sure its not grounded on anything metal

Turned 1 camera on at a time with a DC adapter separate from the UPS. No ground loops bars for all cameras.

Placed all components on 1 Powerstip into 1 outlet.

 

Could I be inducing a ground loop because all of the UPS are grounded inside the box?

 

Also all of the cameras are color. Some turn black and white when more and more are connected. This is an 18 Channel system rated to 10 amps with 1.1 amps on each channel max.

 

Each camera is 500mA and there are 13 DC.

[joseph.chen0312 0]

Better you could use UTP to install all and would be fine