melted/burned coax cable

[damai7788 0]

Hello All,

 

We have a PC DVR System, running almost 6 month, with 16 camera ( 2 x 8 Ch), DVR Card is China brand, PCI slot. At the back side of the card, it use somekind of pigtail, one DB15 to eight BNC port.

 

Installation is using coax cable, not UTP or IP cam. Adaptor/power supply for each camera is plugged near the camera, we bring the 220 VAC near the camera, no POE.

 

Last 2 weeks, one of the camera broken, we replace with another camera, but still no image for that camera, we replace the pigtail, the video is on now.

5 hours later, the camera got broken too.

We replace another one, 5 hours later, broken too. The coax cable output of the camera is melted/burned. Camera have two short cable, one for power/12VDC, and one for camera data/coax. The melted one is the coax pigtail at the camera side.

 

We replace another one, also replace the adaptor.

Within 5 hours, the pigtail (1 to 8 BNC) at the PC side, got burned and melted, make a lot of smoke at the computer room.

 

Almost all cameras is installed at outdoor, all camera is of same type, IR outdoor half egg shape, without enclosure.

 

Anybody please help?

 

Thanks.

[3RDIGLBL 0]

I personally have never seen this. I mean video voltage is so small over coax.

 

Have you disconnected the coax at both end and ohmed out the cable? Not knowing how the cable is run I'm wondering if it is pinched somewhere or being electrically shorted with power somehow.

 

First this I would try is disconnect the coax at both ends and test for voltage on the cable (obviously there should not be any) then I would ohm it out and check for shorts.

 

Others might have a suggestion but thats where I would start. Unless the DVR card is defective and somehow causing this on that one channel. Although if the initial camera was bad and internally shorted it could of damaged the DVR card not knowing if the card had any internal protection.

[damai7788 0]

I though we have found the problem.

 

This camera is installed on an iron pole, lighting pole.

This camera is mounted directly to this pole.

 

This pole is somehow strange. Sometime (not always) it could contain really high voltage electricity, sometime it is not. I think this is related to some machine running in the factory.

 

We have isolated the camera from this iron pole, using wood material, so the camera did not touch the iron pole.

 

Hope this can solve the problem.

 

Btw, the pole is stuck to ground/earth/concrete ( we don't know the pole depth under the ground). if there is electricity there, would it go to the ground, rather than to the DVR side?

 

One more thing, the camera is mounted somewhere, leaving the camera plug to the coax cable, but the adaptor is not plugged to the camera. Unplug the coax from the DVR card pigtail. Using test pen to test the coax cable at the DVR side, the surrounding braid and the center core, sometime one/both of them would contain electricity (the test pen will bright on), is this normal? is this dangerous? must be avoided?

 

Thanks.

[bpzle 0]

I never use voltage detector test pens. They are unreliable and sometimes too sensitive to isolate where voltage is present. Use voltmeters to ensure the presence of voltage.

 

The first thing I would do is disconnect both ends of the coax run and make sure the BNC connectors are not touching anything metal. Use a decent voltmeter and switch it to AC. Use the black test lead to find a ground on the pole somewhere and use the red to test both the braid and the dielectric (core) of the coax. Test with the pole light on, and off. You should not see voltage of any kind. If you do, you have a short to line voltage.

 

I would also switch the meter to ohms and check for resistance to ground on both the braid and the core of the coax. You should not see any resistance going to ground on either the braid or dielectric of the coax. If you do, your shorted to ground somewhere.

 

Next, make sure that your getting 12vDC or 24vAC (whatever the camera uses) from the power supply. I would also highly recommend fusing the output of the power supply with a fast acting 250ma or 500ma fuse.

 

Lastly, but probably the real issue, it sounds like there is a problem with the line voltage at the pole light. There's too many possible issues to list, but either way only a QUALIFIED ELECTRICIAN needs to troubleshoot. High voltage is not for amateurs and ESPECIALLY malfunctioning high voltage.

 

So, you can either A: get slammed with the service bill from a decent electrician or B: remotely power the camera from a known working power source.

 

I would definitely chose option B. You ran coax, I'm assuming you could easily run low voltage power (18/2).

[hardwired 0]

I think we've overlooked suggesting that someone should fix the pole electrical problem before someone leans against it in the rain, and it kills them?

[bpzle 0]

I think we've overlooked suggesting that someone should fix the pole electrical problem before someone leans against it in the rain, and it kills them?

 

 

I don't believe anything was mentioned to indicate THAT sort of electrical problem. From what I gathered, the problem sounds related to sharing the pole's 220vAC with the camera's power supply.

 

HOWEVER, safety should always be a concern. Make sure the pole and electrical enclosure for the light are both properly grounded. If not, YOU will become the ground. Not good.

 

Working around high voltage can be dangerous without the proper knowledge and experience. When in doubt, hire a professional.

 

Cover my travel expenses and I'd be more than happy to assist further.

[hardwired 0]

I think we've overlooked suggesting that someone should fix the pole electrical problem before someone leans against it in the rain, and it kills them?

 

 

I don't believe anything was mentioned to indicate THAT sort of electrical problem. From what I gathered, the problem sounds related to sharing the pole's 220vAC with the camera's power supply.

 

HOWEVER, safety should always be a concern. Make sure the pole and electrical enclosure for the light are both properly grounded. If not, YOU will become the ground. Not good.

 

Working around high voltage can be dangerous without the proper knowledge and experience. When in doubt, hire a professional.

 

Cover my travel expenses and I'd be more than happy to assist further.

 

I'd think it WOULD indicate that kind of problem... at 220vac, you only need 50-100ma to kill, and I'm sure it took a lot more than that to melt a DVR harness. If the transformer he used had a short between the primary and secondary, it COULD cause that problem.. but I'm still betting on a open neutral, shorted photocell,or something of that sort, at the pole, coupling 220vac onto the cam shield... NOT safe... Just check it out, is all I'm saying.