Strange problem when switching from 12VDC to 24VAC

[claptrap 0]

Hello everyone. I've been lurking for some time now but this is my first post.

 

I'm new to the video surveillance world but about a year ago I installed a Dahua analog DVR with 3 Pelco ICS110 DNV9 cameras. I initially powered the cameras using an Altronix 12VDC power supply but these cameras can run on either 12VDC or 24VAC. I live up in Montreal, Canada where the winters can get pretty brutal. Unfortunately, the heaters in these cameras require 24VAC to operate so I purchased a 24VAC power supply to get some heat in the cameras. As soon as I switched the power supply from 12VDC to 24VAC I noticed a very peculiar thing in the video feed on all three cameras. The image is now shifting(jumping) horizontally from left to right and right to left several pixels at a time. Sometimes there is no shifting in the video for several minutes but then it starts up again. This shifting is large enough to trigger the motion detection on the DVR causing it to record almost constantly. I switched back to the 12VDC power supply to make sure it wasn't a camera related problem and the shifting disappeared. Unfortunately, I now have no heat in the cameras. Has anyone ever seen this before and what is causing it?

 

Thank you

[the toss 0]

Is it happening with ALL cameras? The only difference between 12V DC & 24 V AC cameras is that the 24V AC cameras have a circuit built in to rectify/regulate the 24V AC to 12V DC. So really all the cameras internals are 12V.I have found that the weakest part of the 24V cameras is this regulator board ( usually fat caps). About 80% of faulty 24V cameras can be salvaged by bypassing this regulator & running them on 12V.

[claptrap 0]

Thanks for the quick reply. Yes, the shifting is happening on all the cameras so the problem can't be with the cameras. Is it possible that it could be caused by an incorrect polarity connections at the power supply or maybe a faulty power supply? I know that the proper polarity is important when using 12V, but is this also true for 24V AC?

[shropna 0]

This can be Line Lock issue. If you have "noisy" AC power (this can be caused by another electrical equipment in building or if you use UPS with not clear sinus output), just disable Line Lock function in camera.

[the toss 0]

Thanks for the quick reply. Yes, the shifting is happening on all the cameras so the problem can't be with the cameras. Is it possible that it could be caused by an incorrect polarity connections at the power supply or maybe a faulty power supply? I know that the proper polarity is important when using 12V, but is this also true for 24V AC?

 

There is no polarity when operating on 24V ac. Since it is happening on all cameras then it is obviously something common to all cameras. That would be either power supply , or the DVR itself. Just power up one camera & see if it still happens. I would suspect you have a crook DVR.