Barryvdw 0 Posted June 6, 2012 Hi Guys.. I have 25 KPC 172 Cams ( Little Gems these BTW) http://avtechsurabaya.com/cctv/kpc-172-high-resolution-camera.html I am using Passive Baluns and Cat5, but alos Mil Spec Rg59 with Power. Longest Cable Run is about 100 Meter When I use a little stand alone single 12v Power Supply I get clear picture to every camera. When I hook them up to the 9Way and the 18Way power Supply I get a Horizontal Flickering on the Screen. http://www.digitalwitness.co.za/PDF_files/PS9-500.pdf http://www.digitalwitness.co.za/PDF_files/PS18-500.pdf Any Suggestions ..... ??? Share this post Link to post Share on other sites
Soundy 1 Posted June 6, 2012 Does it do that with the RG59 as well? Symptoms sound like a ground loop caused by the combination of a shared power supply, baluns, and cameras with shared video/power ground... very common issue with cheap cameras that have a shared ground. Share this post Link to post Share on other sites
Barryvdw 0 Posted June 6, 2012 Yes the RG59 does have disturbance as well, but not no much horizontal...but definitely a disturbance Why does the 12V 1000 Ma single supply work perfect... Also did remove the earth connection from the mains to power supply but still the same ! Share this post Link to post Share on other sites
Soundy 1 Posted June 6, 2012 Yes the RG59 does have disturbance as well, but not no much horizontal...but definitely a disturbance Does that also go away when you use the separate power supplies? Why does the 12V 1000 Ma single supply work perfect... If the problem is what I expect it is... A ground loop occurs when you have two or more signal-ground paths that are at different potentials. In a camera, your main signal ground would be via the coax shield, or with baluns, via the wires connected to the BNC shields - if this is the only signal path, all is happy. What happens when you have a camera with common power/video grounds and a common power supply is, you then add more separate signal paths: one normal one via the camera's shield, and another via the camera's power ground, into the power supply's ground rail (NO relation to the power-line earth, it's just a common connection for all the outputs), then back to another camera via ITS power ground, and back to the DVR via that camera's signal ground. Normally the difference between these two paths is very small and thus not a problem... however, if you have the wrong type of coax (foil shield), or a poor shield connection anywhere along the way, or defective coax, or are using baluns (which effectively put a wire coil inline with the signal, thus adding substantial DC resistance), you then have a significant, maybe even measurable difference between the two paths... and you get the classic ground loop. Add more cameras with the same difference, and the problem gets worse. When you use a separate power supply for each camera, you break the multiple paths, as each camera then has its own power ground separate from all the others. The issue tends to be worse with baluns because of how they work, but as you see, it CAN happen with coax as well. Also did remove the earth connection from the mains to power supply but still the same ! Yes, because it has no relation to the particularly problem. Share this post Link to post Share on other sites
Barryvdw 0 Posted June 6, 2012 Yes, the problem also goes away on RG59 when I use a single power supply. How would I remedy this ? Share this post Link to post Share on other sites
Soundy 1 Posted June 6, 2012 What sort of RG59 are you using? If it's not solid-copper-core, solid-copper 95% braid shield, that's part of the problem. Best fix IMHO is cameras that don't cheap out with common grounds - something with a built-in regulator, or dual-voltage support. Eliminates the problem right there. Share this post Link to post Share on other sites
Barryvdw 0 Posted June 7, 2012 Cant replace 25 cams ... Help ! Share this post Link to post Share on other sites
Soundy 1 Posted June 7, 2012 What are the markings on the RG59? Suggestions: - check all your terminations - use better-quality RG59 - use ground-loop isolators - use individual power supplies - live with it Share this post Link to post Share on other sites
