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Random lines and jitters in image
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| rvella |
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Posts: 13
Joined: 22 Dec 2006
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Posted: Sun Feb 03, 2008 4:44 pm
Post subject: Random lines and jitters in image
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I installed a new system for a client about 10 months ago. We used a mixture of new cameras and existing cameras. The DVR, power supply, and most of the old equipment was replaced.
Problems started to occur recently. The DVR will show "video loss" on random channels and have frozen images, but this is a separate but possibly related issue.
I'm having lines and random jitters in the image that seem to be power issues. But I don't have a confirmation.
I thought about first putting a UPS on the power source and the DVR to see if bad power would be filtered, and if that didn't help, replace the power supply instead. But I want a second opinion. I've recorded about 30 seconds of footage from the site in order for other people to see.
http://aegisbak.com/f/index.php
If anyone has a solution or thoughts I would greatly appreciate it.
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| crirvine |
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Posts: 240
Joined: 16 Oct 2005
Location: Union City Tn
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Posted: Sun Feb 03, 2008 7:13 pm
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If these are 12 volt dc cams I am seeing a 60 cycle hum or a ground loop problem. What type cameras are they how are they connected to the dvr coax cat 5 has tere been any lightning at the site did you ground the site.
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Thanks Buddy
http://www.pro-tecsecurity.com
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| rvella |
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Posts: 13
Joined: 22 Dec 2006
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Posted: Sun Feb 03, 2008 11:35 pm
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They're a mixture of 12V and 24V cameras. It's a dual voltage power supply. My extent of knowledge on ground loops is limited, but I've always tried to keep the DVR and the power box on the same circuit if that helps.
I've heard of ground loop "blocks" that are meant for multiple cameras. Any suggestions on a particular product? I may just end up replacing the power supply all together.
Suggestions?
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| rory |
Moderator & Founding Member
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Posts: 14214
Joined: 10 Nov 2003
Location: Bahamas
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Posted: Mon Feb 04, 2008 7:43 am
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1-Test each camera on a single power supply at the camera itself plugged into a monitor there. If it still has a problem then its probably a camera issue (bad power board perhaps), or could be ...
2-Remove the camera from the ceiling and see if the problem goes away, if it does, then it may have been screwed into metal, or the cable is running too close to high voltage such as lighting (move the camera and the cable at least 1' away from any high voltage).
3-Try an Isolated Power supply, or try 2 separate power supplies, one for DC and one for AC. Some cameras need to be isolated.
4-Use single transformers on the cameras that are having the problems, if that fixes it, then they certainly need to be isolated.
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BahamasSecurity.com - Bahamas Real Estate - Bahamas Yellow Pages
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| scorpion |
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Posts: 2348
Joined: 26 Mar 2007
Location: Melbourne Florida
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Posted: Mon Feb 04, 2008 11:28 am
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It appears to me in the video that it is a 60 cycle hum.
Does the DVR have a an external power supply, or does it have a straight 120 volt power cord such as a what you would see on a computer?
A UPS/filter will not correct this flaw as the problem appears to be in the power supply itself.
I would start with all of the items Lolo Wolf stated:
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| Kinda tough to make a definitive call without more info, you say radom channels, are any channels not dirty or is it the entire set of installed cams?Looking at your video, I would start by revisiting your terminations and make sure all your fittings are correct (crimp, compression,twist on whatever you employed) doesnt appear to be a ground loop cant really see the screen too well from the sample, the distortion isnt rolling or consistent , What kind of DVR is it (stand alone or PC?) Quick test on site go direct from cam (pick the worst one and observe on a test monitor bypass your dvr input, if that comes back clean then work your way back to the DVR itself and check connects, if they are solid then start to examin your power issues.... DVR power and cam power....voltage, common faults, mains, wire, any new devices thrown into the mix, placement or shared AC etc.. I have seen similar probs with pixel smearing and quick lines of what looks like voltage interfering with image on some PC DVRs that share other video/card devices, but a good place to start would be the hardwire connects first. The frozen images and video loss could be a loose contact or possible that a shield is contacting the conductor causing radom dropoutsand dirt. When cams terminate to a dvr sometimes a internal failure on the imput circuits can cause erractic probs such as yours.. also check and make sure nothing is touching the imputs, (check the actual bnc fittings make sure they are spaced and secure) look for any sources of possible induced ac, pollution. You had 10 months of clean operation, see if any changes have been made onsite, elctrical or tampering. |
There may be a capacitor that needs to be changed in the power supply.
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Scorpion
http://scorpiontheater.com/troubleshooting.aspx
QUESTION: Why is there always enough time to go back and fix it right a second time??
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| rvella |
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Posts: 13
Joined: 22 Dec 2006
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Posted: Mon Feb 04, 2008 10:13 pm
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It happens on every camera, which of course leads me to believe it's the power supply. I'm going to bring in a DC power supply and isolate the AC from the DC.
The power supply in the DVR is internal.
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| dwaitkevich |
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Posts: 9
Joined: 13 Aug 2006
Location: Bristow, VA
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Posted: Sat Feb 23, 2008 2:41 am
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One of the simplest things you can do is take a voltage meter and test the actual DC voltage at each camera location to make sure your getting 12 volts DC. I'm betting at some locations your not. This has a lot to do with the actaul length of the runs for the DC cameras. Even though your using a dual voltage power supply, It's generally not a good idea to mix AC and DC togther. Use a seperate power supply for AC and DC.
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David Waitkevich & Associates
P.O Box 638
Bristow, VA 20136
dave@cameraconsultant.net
www.cameraconsultant.net
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| VST_Man |
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Posts: 1291
Joined: 16 Oct 2004
Location: St. Helena Island, South Carolina
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Posted: Sat Feb 23, 2008 7:53 am
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you might have electrical noise that is caused by another electrical device in the building. During closed hours, have someone watch the pic on the DVR and then start shutting off breakers one at a time. once the pic cleans up, you need to find out what is plugged into that circuit and is causing the noise.
I've seen this before; electric fence chargers, forklift chargers, refridgerators, freezers, dryers, ect.
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"you get what you pay for"
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| kevin.m |
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Posts: 6
Joined: 02 Nov 2006
Location: Jessup Md
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Posted: Fri Apr 04, 2008 9:23 pm
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You have ground loops. The key here is bands, lines or bends that move slowly up the screen. The way a ground loop happens is when you ground a camera on a long run. The long coax shield has resistance. Ohms law tells us if we have a resistance and a current we will have a voltage potential. The current comes from the two different AC grounds. The camera side is at a ground and the head end is at a ground. If these two grounds are at slightly different voltages you will have current flow. The best way to eliminate the ground loop is to take the camera off of ground. You can test for this by letting the camera dangle by the coax. Put a piece of insulating material between the camera and the metal that the camera is mounted to. The ground loop will disappear. The other way is to use a hand held battery operated monitor on the coax at the head end. Since the monitor is not grounded the lines will go away as well. Touch your BNC to a chassies thereby grounding your monitor and there the lines come back. Get the camera off of ground by insulating the mount and use nylon hardware so the mount or the camera to the mount is broken from the ground. You can also use a ground loop transformer. If the ground loop is severe you may have to use more than one. The are installed at the head end.
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