Wavy lines on on DVR monitor, but not on TV

[paulnye 0]

I have wavy lines on the DVR screen, but when I plug the cameras 13, 14, 16 into a regular CRT TV the pictures are 100% clear and perfect.

It cant be a bad signal on all 3 cameras because the picture is perfect on the TV

It cant be that ports 13,14,16 on the DVR are bad because other cameras are 100% fine when plugged in to the same ports/channels

These 3 cameras are all running from one locally powered 12vdc power supply, and the video runs 1000ft over cat5e with baluns.

Channel 15 is an example of a good camera signal. The DVR is a 16Ch Q-See QT-528

 

What could be the problem?

 

[Soundy 1]

Ground loop caused by using baluns with cheap 12V cameras that have common video and power grounds. Put each camera on a separate power adapter and the problem will go away.

[paulnye 0]

Ground loop caused by using baluns with cheap 12V cameras that have common video and power grounds. Put each camera on a separate power adapter and the problem will go away.

1. If caused by the common grounds on the cameras, would the baluns still be at fault?

2. Could you explain why the picture is crystal clear on the regular TV, but wavy only when connected to the DVR

[Soundy 1]

1. If caused by the common grounds on the cameras, would the baluns still be at fault?

The baluns are not "at fault", really... the ground loop is created because each camera has multiple signal-ground paths through the other cameras' power grounds, and they're different DC resistances because the baluns are essentially coils inline with the other signal paths.

 

2. Could you explain why the picture is crystal clear on the regular TV, but wavy only when connected to the DVR

You don't get problems on the TV because you're only connecting one camera to the TV, so that camera only has a single signal-ground path. If you disconnect two of the three cameras from the DVR, the picture on the remaining one should be crystal-clear as well. Reconnect a second one, you'll probably see a bit of noise; reconnect the third and the noise becomes worse still.

 

I've been meaning for months to sketch up a diagram of what's happening to cause this... really should get that done.

 

Ultimately, the "fault" lies in a cheap camera design that uses a shared ground for video and power. Cameras that physically separate the power ground via transformer or regulator don't have this problem.

[paulnye 0]

Actually, one camera at a time into the DVR has wavy lines.

However, I will see what happens when I power each camera separately

[ljarrald 0]

although i understand ground loops, a diagram would be very useful soundy

[Securame 0]

I've been meaning for months to sketch up a diagram of what's happening to cause this... really should get that done.

 

I would also love to see that diagram, indeed!

[Horizon 0]

A likely reason why the TV picture is clear is that the TV isn't grounded. Check its power lead - if the plug only has two pins, then the TV is double-insulated (no ground), so there will not be a ground path through the TV, so no ground loop.

[Soundy 1]

A likely reason why the TV picture is clear is that the TV isn't grounded. Check its power lead - if the plug only has two pins, then the TV is double-insulated (no ground), so there will not be a ground path through the TV, so no ground loop.

That's possible as well, if the picture is still bad with only one of the affected cameras on the DVR.

[Darkoracle 0]

I have a similar issue in that when viewing pictures via the computer or viewing the recorded files there is a sort of phasing rather like camera 'hunting'. It alternately goes slightly out of focus and then back into sharp focus on a second by second cycle.

When viewed live on the TV there is no such phasing and the picture is rock solid and sharp.

However when I view the recorded files through the TV, the phasing is again apparent.

Any ideas?

[ljarrald 0]

i have a similar issue also,

when viewing live on the tv everything is fine. but when viewing live or recorded on the computer software, the cameras seem to flash bright and normal with the brightness. like, one second they'll be normal, then slightly lighter, then normal again.