Parallel Fog Type Lines Moving Up And Down Screen

[jizzer]

Hi,

I have had my home cctv up and running for a few months no problem

I have 3 cams 2 baxal in exterior housings and an exterior ljd dome these all feed into a American dynamics dvr then the output modulated and fed to the tv's in my house.

I have noticed over the last two nights both on live and recorded images the dome cam image has what i can only describe as 2 parrallel horizontal fog type lines about 25mm across running sometimes from top to bottom sometimes bottom to top and at different speeds and sometimes they are stationary.

I have eliminated a faulty channel on the dvr by swapping the cam input from one to 4 but the lines still appear.This is only noticable at night as the image is relatively dark as daytime arrives the foggy type line seem to dissapear but i suspect they are still there and it is just the fact that the scene is bright.

Any suggestions I have rebooted the dvr powered down both camera and modulator but the fault remains and is confined to the dome cam.

I have no experience of Hum bars could this be the cause although the system has been fine for months and I havent added anything or do you think the cam could be on the way out.

Thank you

[jizzer]

hi there

i think you may be experiencing either of 3 problems. Power/Voltage drop, Magnetic field interferance from mains cables, or a faulty cam/ rg59.

first things first. have you checked the voltage at the cam end, and what is the length of run. what have u run the 12v dc to dome in, ie .75mm flex or alarm cable etc? have you tried a new psu? failing the psu have you tried a humbug to remove interferance from the video cable, and are you sure the rg59 coax isnt run along with mains cables. i know this seems as im asking alot very quickly but its the only way to find things out that may be at fault. colin

I have a good quality psu no I havent checked the voltage at dome cam end but cam is only about 4mtrs from the psu while other cams are about 20 mtrs away with no problems unfortunately the rg59 does feed up a conduit to the dvr in the loft with switch wires in also for a light but these are not always live and it has been happily doing this for about 6 months not ideal i know but this fault has just appeared ovenight is there any images of humbars i could look at. the power is supplied via .75mm flex all the rg59 cables have 3 part bnc crimps.

[jizzer]

best thing first to do check the voltage at the cam end as i once had a similar experince and found the psu was low on current so i added a dedicated psu to the cam and hey ts all right now try that firrst then post back if any more help is needed

colin

Will do but not tonite brass monkey weather in Yorksuire today.Ithink I will then direct connect the cam into the dvr with a short length of rg59 and see if the fault is still there.

[Guest]

as above my first suspicion would be the psu for the cams. Just run em on a charged up battery and see if it stops then you will know

Why i always have a charged one at my disposal, its more often than not a pus gone down the swannie.

[Guest]

think you mean psu not pus dont you????

You may be correct there

[arfur mo]

have noticed over the last two nights both on live and recorded images the dome cam image has what i can only describe as 2 parrallel horizontal fog type lines about 25mm across running sometimes from top to bottom sometimes bottom to top and at different speeds and sometimes they are stationary.

I have no experience of Hum bars could this be the cause although the system has been fine for months and I havent added anything or do you think the cam could be on the way out.

Thank you

for me you seem to have got the answer already - hum, the camera earth and the DVR earth are at a different potential, fitting a decoupler filter will isolate the 2 earths from each other. you may need to fit a filter to ALL camera's fed from a different mains source to the DVR as it may be they are connected to different mains phases.

if you want to be sure, and as a temporary measure only to test, dissconect the mains earth from the camera, if the bars disappear then get a hum filter (not expensive). if you just fit a battery it wil cause a false conclussion as you are disconnecting the earth.

regs

alan

[jizzer]

for me you seem to have got the answer already - hum, the camera earth and the DVR earth are at a different potential, fitting a decoupler filter will isolate the 2 earths from each other. you may need to fit a filter to ALL camera's fed from a different mains source to the DVR as it may be they are connected to different mains phases.

if you want to be sure, and as a temporary measure only to test, dissconect the mains earth from the camera, if the bars disappear then get a hum filter (not expensive). if you just fit a battery it wil cause a false conclussion as you are disconnecting the earth.

regs

alan

There is no earth to the camera its a 12vdc supply to the cam I would have thought if there were a hum problem it should have shown up when i first installed the system 6 months ago I know nothing has changed regarding the install as its my house.

[james.wilson]

not always, have you tried the battery idea?

[Map Security]

Interesting reading the issue discussed above as I have an install in a small office and the cable runs will be 50mtrs...I will use a PSU for all 4 cams and use high quality shotgun cable....The runs will be laid under flooring and in some areas there are power cables...some quite large dia......Am I likely to pick up EMC issues as a result?

[james.wilson]

metal trunking?