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faint bands scrolling up the screen

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I have a problem with a recent installation. We have 8 cameras connected up to a geovision system. Tested system in office prior to installation and no problems.


Installed system using 3 * 2.8amp 12v power supplies.


My problem is the view has faint bands scrolling slowly up the screen. The psu's are powered from a seperate circuit from the dis board.


I have tried plugging everything into the same circuit and the problem is still there.


Any ideas?

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A few suggestions for you.


Plug in just three cameras which are powered from the same 12v supply. Hopefully you shouldn't see the problem. (By the way, I'm assuming that the "plugging everything into the same circuit" suggests all three Power Supplies connected to the same AC mains point?).


If you do see the problem immediately, remove the first three, then try two or three cameras powered from one of the other PSU's.


When you have a clear picture with 3 connected, start to add extra cameras - at some point the problem will appear. If it appears with camera 4, remove the cable, and sequentially try each of the others to confirm the problem. If you are able to connect 5 or 6 or 7 without the bands showing, that may indicate just a single camera providing the source of the problem.


If any additional camera plugged in to channel 4 creates the problem, that indicates a power supply issue (albeit that there may be nothing physically wrong with the PSU). Should you be able to plug in 5 or 6 cameras before the problem appears, that may suggest a specific PSU is the source of the problem (swap the units over to confirm, or provide a replacement).


If the problem still exists and you haven't managed to trace it, you'll need to post some more detailed info. on the general appearance of the 'faint bands', cameras, transmission (particularly cable paths), etc.


Wish you luck!

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Thanks for reply


I have tried using my test screen at each camera to rule out the co-ax cable and the lines are visible on the test screen.


I have mounted my 3 power supplies next to each other, could they be interfering with each other and cause the problem??



They are near the main distribution board, could the interference be from that?

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If you want to trace the cause of the interference, you are going to have to 'break down' the system, and reconnect bit by bit until the problem re-appears.


It may be a pain in the a**e, but their really is no short cut.


The power supplies may well have caused the problem, but unless you isolate key components one at a time, you won't get anywhere fast.


Incidentally, when you tested the video out on each camera, were the power supplies disconnected from all the other cameras, or were you still powering 3, and testing them one after another?

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