Omega Owners Forum
Chat Area => General Discussion Area => Topic started by: mv6copcar on 30 October 2008, 07:40:37
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un-related to cars.
Got an issue with my TV. I've got these lines scroling up the screen, been told its call 'hum' caused by differing voltages in the grounding cables around the TV and componants,(sky box, dvd,wii etc)
I've moved all the video cables away from any mains cables and made sure they don't cross eachother, but still no different.
It's more noticable when theres dark/black screens shown, even watching the footie,the green of the pitch shows the lines quite clear.
I've earthed all equipment to the same ground.
I can't seem to find any type of 'ground loop' isolators anywhere!!
Anyone else have this issue / had this issue?
Cheers :-[
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No, but have had other issues when devices like washer / dryer / heating / shower turn on or off.
They used to upset an old DVD player, cause PC issues.
Sorted them all by using these Surge / Spike / RF protection extension leads, Belkin and a few others do em....
Sure most the claims on the box are rubbish, but did solve my interference issue.
May be worth a try
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No, but have had other issues when devices like washer / dryer / heating / shower turn on or off.
They used to upset an old DVD player, cause PC issues.
Sorted them all by using these Surge / Spike / RF protection extension leads, Belkin and a few others do em....
Sure most the claims on the box are rubbish, but did solve my interference issue.
May be worth a try
Thats sudgesting a wiring fault somewhere!
Or if a single device then an issue with the internal suppresion.
As for ground loops...I am not convinced.....does it still occur if viewing say an RF video source (video recorder), does it do it on all channels, is it only on aux or scart?
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I've tried unplugging all cables and just connected the sky to the tv, much better but still there, then i plug the dvd player in, getting worse, plug the wii in, worse still, and with the cctv plugged in as well, totally unwatchable (constant bars rolling up picture)
PS i'm using a 4way remote controlled RCA selector to switch between different inputs.
the TV's mounted on the wall with a single Video RCA connected, Audio L+R RCA's go to the surround sound.
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And everywhere i look on the web i find 'ground loop' isolators for audio, but none for visual..........must be something out there
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SOunds like poor cables to me and you should be using a Scart selector as RCA is rather poor anyway
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SOunds like poor cables to me and you should be using a Scart selector as RCA is rather poor anyway
cables are 'cambridge audio visual' screened and gold plated, and the reason for rca is that the wii has triple phono output, the cctv has bnc (with convertors to phono) and the sky has the option for rca, so it was easier.
would using a scart selector with 2scart-to-rca adaptors be better?
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Agreed, sounds like poor cables....and just because you have some over rated cambridge audio gold plated, million strand conductor, oxygen free copper stuff......dont assume they have a good screen in them.
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Are you sure the ground in your building hasnt been knocked out? :(
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Are you sure the ground in your building hasnt been knocked out? :(
:o checked that, and its ok. good job too ay!
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Are you sure the ground in your building hasnt been knocked out? :(
:o checked that, and its ok. good job too ay!
phew! :y
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Agreed, sounds like poor cables....and just because you have some over rated cambridge audio gold plated, million strand conductor, oxygen free copper stuff......dont assume they have a good screen in them.
well i can see what your saying but i've tried to get the best gear i can, in total all the cables i needed came to £185, been re-asured by the shop that sold them to me it wont be caused by the cables.
am pulling my hair out at the mo!!!!!!!
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Have a look here:
http://en.wikipedia.org/wiki/Ground_loop_(electricity)
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Have a look here:
http://en.wikipedia.org/wiki/Ground_loop_(electricity)
cheers mate, but been there befor, and yet again they talk about a loop isolator. i've earthed all equipment to the same ground.
just got to find where to get these isolators!
:-/
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Have a look here:
http://en.wikipedia.org/wiki/Ground_loop_(electricity)
cheers mate, but been there befor, and yet again they talk about a loop isolator. i've earthed all equipment to the same ground.
just got to find where to get these isolators!
:-/
If you scroll down it talks about low amp devices causing an imbalence of ground voltage which could be causing the issue. If you have a different screen try using that and see if the results are similar.
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Right
1) How many of your items (in this setup) use the earth pin.....I suspect none (as is common on double insulated items these days) so ignore the mains earth.
2) Do you get interference with a single link from the a piece of equipment to the TV, in this scenario you cant have a ground loop....
The princpile of lopps should be overcome by your switch box as this should be the star connection point in the setup.....with the TV and ancillaries being the leaf and route points.
Is there a TV earial lead connected to the TV via another pice in your setup?
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I also doubt it's a ground loop as such because 99% of this type of equipment is double insulated and doesn't have a ground connection from the mains supply. This means your only ground connection between the units is via the signal cables, and this ties all the grounds to the same potential. You should probnably avoid trying to connect other grounds to the devices as this is exactly what causes a ground loop.
These are classic symptoms of mains hum getting into the video signals, however.
My money is on either poor screening of the cables, or a poor connection of the screen as it enters one of the appliances.
Another possibility is that the power supply of one of the devices is breaking down and either passing "mains hum" into its' DC outputs and affecting the quality of signals passed through it or, more worryingly, the isolation between the mains and output is breaking down and causing leakage of AC current.
As Mark said, it's key to determine of this "hum" is present on the picture with only an RF source into the TV directly from the antenna. If it is present, it points to a fault in the TV. When it is preseny, is it present with all source signals, including the TVs internal tuner, or only those connected
Next, try different combinations of peripherals connected and see if there is a pattern. As you have said, it's good practice to separate the signal cables from mains cables and also from devices such as mains adaptors which contain transformers.
Many external switches for video are pretty poor quality. Can you not connect the devices to SCART sockets on the TV and switch them internally? You will benefit from a better picture as this avoids PAL encoding and you can eliminate a component from the system.
The reason you don't see many "braid breakers" for video signals is that the audio devices are just a transformer. Since video signals require frequency response down to DC, and very good transient response with no "ringing", isolating a video signal is an order of magnitude more difficult.
Another thought. You talk about CCTV? Is this a wired system? If so, could it be that the video signal from this is grounded at the remote end of a long cable?
Kevin
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if you plug them in without the RCA do you still get interference?
I was getting screen interference and it was my scart splitter causing the problem
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I use one of these and the picture is great.
Composhite is always a last resort signal, always try to use RGB or component
http://www.vtx.co.uk/video/trilogy1.htm
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(http://www.vtx.co.uk/images/Trilogy1.jpg)
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Just try a different telly.
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Thanks to everyone who helped out on this one - i had the engineer visit me from the shop where i brought all the cables and adaptors from, Get this - - The scart switching unit i use (same as pictured above) has a 12v dc tranny (built into the plug) this was leaking ac signals everywhere, when turned on he picked up static from the other side of the room!!!!!!!! :o :o :o
the second he unpluged it - perfect picture.
so even though everything i could disconnect was disconnected, the plug 12v tranny was still emitting noise/signals.
SORTED! thanks again people! :y