looks great on Monitors, but not through DVR

[CraigVM62 0]

On a remote building I have two cameras. One being a basic Speco Armored Dome, the other a Toshiba Box Cam and Lens in a non heated enclosure.

 

DVR and Power supply is around 280 feet away via twisted pair and passive baluns.

The problem is both cameras look great when fed directly to any of several portable and standard monitors I have.

When fed into the Kaltech / Digital Watchdog DW-4ZAPro DVR, one camera is having problems.

The dome camera still looks great, but the nicer Toshiba box camea looks like a scrambled cable TV channel from back in the 80's, except the lines are horizontal.

I have tried plugging it into a different inputs but the scrambled image follows that camera.

 

I checked the voltage reaching the cameras and found it is only 10.6 volts. By the camera not getting it's normal 12 volts, would it's video signal not be as strong? Guessing the DVR needs a stronger video signal than the monitors need be happy

Correcting the voltage problem will be an easy fix. If this is not the needed cure, I was wondering if anyone has experienced this problem and what they found. Thanks for any input you may have.

[scorpion 0]

I do not have much experience with the cat5, and baluns.

 

What you are describing sounds like a bad balun. I have seen this and only had to change out a bnc to rca adapter. I am only taking an educated guess in your case.

 

What I really suspect is that you have a ground loop problem. Are the cameras Isolated from the building? I assume it is a metal building?

 

When you hook up a test monitor to the camera you are bypassing the ground loop issue, or a bad balun issue.

[survtech 0]

The voltage is a little low. Most authorities recommend no more than 10% drop. You have nearly 12%.

 

But that still doesn't explain why you are getting a useable picture on a closer monitor. Check your connections. Make sure your baluns' + and - are connected to the same color at each end. Try powering the camera locally.

 

Bad baluns are extremely rare and 280' is well within the distance limitations for passive-passive. If you can, try swapping cables between the two cameras. If the problem follows the cable, that's the source; if it follows the camera, that's the source.

[CraigVM62 0]

My fingers are crossed that it is the voltage loss issue. If that does not resolve the problem. I will also take the suggestion of replacing the baluns on the problem camera.

I don't think it is a reverse polarity problem with the baluns since they have a great image when fed directly into a monitor.

I am pretty certain that when a balun is hooked up with the polarity reversed, you won't get anything close to an image.

The buildings are metal, so I isolated the cameras when I originally installed them to avoid any ground loop problems. Still I will confirm that by checking for any continuity between ground at the monitor / DVR location and the Baluns.

 

Thanks

[scorpion 0]

If it was a ground loop, you could confirm it by disconecting the camera from it's mount, or by removing the camera itself.

 

If you have preisolated the cameras then do as Survtech suggested by using an extension cord, and powering the cameras locally.

[survtech 0]

If you're certain the polarity of the baluns is correct, more than likely the problem is weak sync which usually indicates high resistance or a major impedance mismatch.

 

You can test polarity by reversing the wires at the balun on one end. If the picture becomes viewable, you had the polarity reversed at either end.

 

With twisted pair, it is not important that any specific wire is (+), just that at both ends the same wire is (+).

[scorpion 0]

There is a way to test if it is a GL issue.

 

Find a product similiar to this:

 

http://www.vsscctv.com/ProductDetail.asp?ProductID=492

 

Let us know when you get it solved.

[CraigVM62 0]

You guys kept pushing towards it being a Ground Loop problem, and you nailed it.

I was 'certain' that I had eliminated any chance of the housing being grounded to the building. Originally a DVR was installed on the opposite end of the same building, and I had a GL problem. I corrected it by mounting the housing bracket onto a 8" x 8" piece of 3/4" Plywood. I used bolts and recessed the heads in the plywood so they would not make contact with the metal building. I then anchored the plywood to the building with screws. This resolved the problem

 

There was a down time of a few weeks when the DVR was removed and cameras were not being viewed. At the end of that downtime, A new DVR was installed in a different building and when it was fired up, that is when the problems this tread addressed came about.

 

During that downtime, we had a good amount of rain so water was absorbed by that piece of plywood, allowing it become something of a conductor. The new DVR location was now in a different building with a completely different electrical service and meter. That small amount of continuity the wet plywood was causing seemed to go a long ways.

This all became clear when I finally took your advise Scorpion and just pulled the cam from the housing. I know that is one of the most elementary methods to trouble shooting a potential GL problem, but I was just convinced my "plywood fix" had eliminated it from being a possibility.

I will learn to listen better and sooner

 

Thanks for your help

[scorpion 0]

AMAZING!

 

I NEVER WOULD HAVE THOUGHT OF THAT!

 

Ground loop through wet wooden mounts!

 

Now I have a new trouble shooting tool to add to the mental toolbox!

 

Thanks for the feedback!

 

Once the wood dries out what will you do? Paint the wood with Kills primer, and some paint?

[survtech 0]

Not so amazing. I've seen ground loops through wood telephone poles.

[CraigVM62 0]

In hindsight, it was a big "DUH" on my point for not considering the issue with the wood getting wet. The plan was "after it stopped raining" to paint the plywood if not just for cosmetic reasons.

 

I ended up using a nylon bolt and some rubber washers to isolate the camera from the housing.

 

I am thinking that in the future I am going to avoid metal housings all together and stick with the better "non metallic" versions.

[rory 0]

Or use plastic instead of wood in the future

[CraigVM62 0]

Hey Rory,

 

I don't know where I would find chunks of plastic thick enough though. On one of my larger installs "large for me anyway" I used these APW / EMI Housings. The entire Housing is made of a very strong Polymer Plastic so the camera is completely isolated from the metal bracket and mounting surface. That install is a year old and they have held up perfectly.

Anyone have any long term experience with these housings. I wonder if they discolor at all after years in a very sunny environment.

 

[rory 0]

I like the ABS plastic ones myself over metal ..

 

But you should be able to find a plastic store somewhere, that cut plastic to any size and in various colors; we even have "one" here

[chad_cooper 0]

One easy way to check for ground loops that doesnt take you up to the housing. use a 2prong adapter at the drv and monitor side of the system and see if it takes out the issues. This is removing ground from one side of your system and will tell you righ away if it is a GL issue.

 

Hope it helps.

[rory 0]

Hi Chad, whats a 2 prong adapter?

 

Thanks.

[UMDRanger 0]

Rory -

 

On a lot of older US homes the outlets only have the AC vertical slots, so you may need to use a 2 prong adapter to plug in your normal AC with ground pole plug.

[chad_cooper 0]

Ranger,

 

Exactly, this will "lift" the ground from one side of the equipment. ( of course I would never tell you to leave it there, as that would void the UL ground )

[rory 0]

Ahh, ok thanks .. makes sense .. get rid of the ground ..