Ground Loop Issue?

[Fahad Abrar]

Hi all

 

I have come across this for the first time in my five years of cctv installations.

 

Here is the set up;

 

4 cameras (TVI - from GTec)

TVI DVR from same company

Coaxial Cabling (shotgun)

Cameras powered with a 5A compact (adapter) power supply at the destination (i.e. same place where the DVR is located)

 

Location of DVR and where all the cabling lives; in the loft of a bunglow.

 

Output is completely teary and full of interference; see picture attached.

 

Now I have been in contact with the supplier and they have advised us to carry out few tests and none of them seem to have worked so far:

 

1. At some places our coax cables were first running along the 220V electricals which the company thought  was the major cause of interference. To remedy that we re-routed the wiring, i.e. made sure that it is 'completely' away from the 220s, and the closest we have ever got to a 220v with our cables runs is half a feet. Unfortunately the result is the same level of interference.

 

2. They asked us if by powering up the cameras individually using separate power supplies will fix the issue but using individual power supplies doesn't ever power up the cams.

 

3. We see output on the screen only in the case when ALL FOUR cameras are connected to 1 to 4 way connector lead. if you disconnect one or two from the lead then all the others do not show any video output

 

3.1 Also tried the boxed 10A power supply, same issue persists!

 

4. One of the 4 cameras doesn't even switch on, it comes on briefly for a second and then goes. This cam is the farthest away from the DVR 15 meters i suppose.

 

5. Now this is the reason I think it is a ground loop issue; I can feel a tingle on the BNC connectors at the back of the DVR when i touch them and of high intensity.

 

6. So keeping the above point in mind I decided to order some humblocks from systemQ,

http://www.systemq.com/cgi-bin/commerce.exe?preadd=action&key=CON700

 

connected all of them up but there is NO video output when they are connected ( The sales guy at systemQ clearly said that these will work with TVI cameras, is there a compatibility issue here?

 

My back up plan is to switch to analogue cameras and then use the humblock with them.

 

Really do not have any other ideas, can anybody suggest anything please? (

 

Thanks

Fahad

[Adi]

Polarity reversed on one of your connections.

[sixwheeledbeast]

I can't see it being a ground loop. Most likely a PSU or supply issue, maybe even the camera you mention not working dragging the others down.

 

Humblocks only mask an issue and are not really fixing it.

[Belfastengineer]

I didn't think humbugs would work on TVI. What are the cameras fixed to?

Edited March 14, 2016 by Belfastengineer

[Adi]

but tvi is analogue, would the humblocs not allow the signal through.

[Rob Kirk]

Anything earthed at both ends that shouldn't be? not that there sounds like anything needs to be but sometimes there is.

 

Are you sure when using separate psu's you have the correct rating to power the cameras?

 

A lot of those 5 amp compact psu's are ****!

 

Was the cable of good quality, have you used it before to good results?

Edited March 15, 2016 by Rob Kirk

[ElecTech]

Disconnect one coax at a time until the other 3 pictures become clear, you've then narrowed the issue down, then do the checks above...

[al-yeti]

Seems to me you need to remove the DVR, PSU and one camera and test on bench

In point 2 and other places it doesnt make sense , how can you not be able to power one camera ?

Edited March 15, 2016 by al-yeti

[Fahad Abrar]

Adi: Surely reverse polarity won't even power up the cameras? I did notice that one of the connectors was put in with reverse polarity but fixing that still didn't sort the issue out. Does that permanently damage the cameras or the cabling? I will however recheck. And that's what was told to us about humblocks that they will work with TVI.

Sixwheeledbeast: if one of the cameras is not working then when we tried powering up one after the other that problem would have gotten picked up. I will actually try some more combinations.

Rob: yes the supplier did acknowledge that a type of PSU doesn't work well with TVIs so they sent us another one but unfortunately it's the same result. Yes we use that cable all the time and with good results.

Al-yeti: yes I think I need to take it back into lab.

Yes, that's the puzzling part that cameras don't power up with individual power supplies.

[J&D Security]

It sounds like a power problem to me, what are you reading under load at the cameras. Are the cameras dual voltage? If so try an AC psu.