Ground Loop or other voltage issue?

[wick1144 0]

I replaced an old DVR with a new HD TVI DVR. All cameras worked on the old DVR. After connecting to the new DVR, four of the 16 cameras worked. The remaining cameras did not. I did some troubleshooting and found that there is 32-33 volts AC on the meter when I test between Coax shield and DVR (testing at the BNC camera input ground). I also tested between coax shield and ground on outlet (third prong) and got the same. I've never seen this before. The four cameras that work, do not have this voltage. I've heard of ground loop issues, but this is a lot of voltage. This is a five story building and cameras are powered at outlets at the camera site, not at the DVR site. I don't know if a ground loop isolator would work on that much voltage. Besides running new power cables from cameras to head end, are there any suggestions.?

[tomcctv 190]

Hi. Did all cameras work before ?

IF groundloop was needed you would still get a image.

 

Why are you testing coax with AC ?

 

Have you moved a working camera to a none working port

[wick1144 0]

All of the cameras were working before I switched the DVR. I didn't move or change anything other than the DVR. I was checking for ground loops and any voltage issues that could affect the video and found the voltage. I figured that the newer HD capable DVRs may be more sensitive to electrical issues.

[tomcctv 190]

All of the cameras were working before I switched the DVR. I didn't move or change anything other than the DVR. I was checking for ground loops and any voltage issues that could affect the video and found the voltage. I figured that the newer HD capable DVRs may be more sensitive to electrical issues.

 

 

Still does not matter even if a ground loop problem you would still get a image.

 

You don't test coax with AC

 

 

Did you try moving a working camera to a port that is not displaying anything ??

[wick1144 0]

Yes I moved cameras to different ports. All cameras with the voltage issues did not work on any port. Cameras without voltage issues worked on all ports

[tomcctv 190]

33v ...... How are your cameras powered

[wick1144 0]

Powered locally at camera, not at DVR location. 12vdc transformer

[tomcctv 190]

Powered locally at camera, not at DVR location. 12vdc transformer

 

 

So we're do you think the 33v is coming from ???

 

No point you testing AC voltage on a DC system .

 

Also all analog cameras put voltage down coax

 

 

What dvr are you using

[wick1144 0]

The only thing I can think of is the difference in grounding effectiveness between the ground at the DVR location and the ground at the camera location. This difference in grounding effectiveness would result in voltage. That's my guess. That's why I'm looking for help. I've been doing this for over 20 years and never saw this before. But I never really looked.

[tomcctv 190]

The only thing I can think of is the difference in grounding effectiveness between the ground at the DVR location and the ground at the camera location. This difference in grounding effectiveness would result in voltage. That's my guess. That's why I'm looking for help. I've been doing this for over 20 years and never saw this before. But I never really looked.

 

 

20 years ...... You should know you would still get an image . With ground loop

 

Ground loop would of also of been on last cameras

 

Which dvr do you have ?

What type of cable

What length of cable

What power to each camera

[wick1144 0]

Which dvr do you have ?

Truvision TVR15HD

What type of cable

RG59

What length of cable

Varies 30-100'

What power to each camera

12vdc plug in transformer.

[wick1144 0]

I have had ground loop issues that we're not on the last camera. On the newer DVRs, at least this brand TVI compatible DVR, the ground loops can completely eliminate the picture. Much more sensitive.

[tomcctv 190]

I have had ground loop issues that we're not on the last camera. On the newer DVRs, at least this brand TVI compatible DVR, the ground loops can completely eliminate the picture. Much more sensitive.

 

 

You need to get over it’s a ground loop problem and can I just point out your cameras are individual powered SO AGAIN not a ground loop.

 

 

You need to sit and read the manual it only took me 5 mins of reading it to see what your problem could be .

 

Displaying 4 cameras only ...... I’ll give you a clue A or B

 

Don’t mention ground loop

[wick1144 0]

ok Maybe I didn't explained the issue incorrectly. The display is showing 16 camera windows. I am only getting video on 4.

[tomcctv 190]

A or B

 

Video output on that dvr according to manual

A is full live view of all cameras 1-4-8-16

 

B is spot output .... output is picked by user ... in your case only 4 cameras have been selected 1 can view will only show first cam .... 4 camera few will show all 4 cameras selected for spot .... 8 camera view will show your 4 spot cameras plus 4 blank and the same with 16 it will show the 4 selected as spot plus. 12 blank.

 

You need to go into monitor output settings and pic live view and disable and not use spot view

[wick1144 0]

No. It's not the display settings. Not quite that basic. Wish it was. Thanks for the thought.

[tomcctv 190]

No. It's not the display settings. Not quite that basic. Wish it was. Thanks for the thought.

 

 

Still not answered the question are you on A or B.

 

 

Also how many cameras show on local view over PC

[wick1144 0]

To make a long story short, I eliminated the voltage on the coax shield by running power from the head end to the cameras putting everything on the same circuit. The non-working cameras had to be replaced. Just wondering if the AC voltage on the coax shield had anything to do with the camera failure.

 

Thanks for your input, but turning the page on this.

[tomcctv 190]

To make a long story short, I eliminated the voltage on the coax shield by running power from the head end to the cameras putting everything on the same circuit. The non-working cameras had to be replaced. Just wondering if the AC voltage on the coax shield had anything to do with the camera failure.

 

Thanks for your input, but turning the page on this.

 

So not a ground loop problem ..

 

 

Did you find out how your getting AC on your coax ??

 

Or could it of been a faulty multimeter or your using wrong setting.

 

You stated earlier in a post your using 12vdc ..... and coax will have some power and that will also be dc which is normal .

[wick1144 0]

I don't know how the voltage got on the coax. Once I placed all power in the same circuit, the voltage was eliminated. I guess a grounding issue in the building between the 5th floor and floors 1-4. Meter works fine.

[wick1144 0]

I know that DC power is on coax, but at very low voltage. Millivolts, not 30+ volts.