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Author Topic: VGA HUM ELIMINATION  (Read 14040 times)

Corne Stapelberg

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VGA HUM ELIMINATION
« on: February 14, 2011, 08:27:10 am »

Is there a VGA HUM ELIMINATOR on the market?
What do you use to eliminate hum assosiated with VGA images?

Regards
Corne'









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Brad Weber

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Re: VGA HUM ELIMINATION
« Reply #1 on: February 15, 2011, 07:15:31 am »

The best solution is to find and address the cause of the hum. Otherwise:

http://www.extron.com/product/product.aspx?id=gli2000&subtype=45&s=4
http://www.jensen-transformers.com/datashts/vbh5bb.pdf

You may have to use HD15 to 5 BNC breakouts if you're not already running five wire cable.
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Justin Dodd

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Re: VGA HUM ELIMINATION
« Reply #2 on: February 17, 2011, 02:32:59 am »

The Extron units seem to work pretty well, though they dont always completely fix the problem. Usually helps when all the video devices are coming off of one power source.
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Keith Broughton

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Re: VGA HUM ELIMINATION
« Reply #3 on: March 14, 2011, 04:32:31 pm »

Is the hum visible on all displays or just the projectors?
Hum bars are a visual display of a ground loop.
The most common one is between control and the projectors. Also from cameras to control.
Disconnect all the power cables from the projectors/cameras and add them one at a time until you see which one(s) are causing the problem.
You can use an AC plug ground pin lift to test and see if the problem goes away.
Also, make sure when you are mounting projectors to a truss that you use some gaff tape to isolate the clamp from the metal truss.
Sometimes an audio connection from a mixer to video control can be the problem. Use isolation transformers on audio feeds.
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Jonathan Bright

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Re: VGA HUM ELIMINATION
« Reply #4 on: July 16, 2011, 09:34:33 pm »

Is there a VGA HUM ELIMINATOR on the market?
What do you use to eliminate hum assosiated with VGA images?

Regards
Corne'

I believe you are talking about hum that occurs when you have a computer with a stereo plug out into your sound console and a VGA cable also connected to the same computer.  You probably noticed that when you disconnect the VGA, the hum goes away, so you isolated it to the VGA.  This is the exact scenario I had a couple of years ago.  Our solution:  We took a stereo plug to 1/4" and ran it into a DI box (Whirlwind IMP 2) and then ran the XLR from the DI box to the sound console.  Use the ground lift on the DI Box and the hum is eliminated.
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Greg_Cameron

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Re: VGA HUM ELIMINATION
« Reply #5 on: July 18, 2011, 03:59:47 pm »

If you're in a situation where the projector(s) are far from the source video and you cannot feasibly get power to the projectors on the same circuits or sub panels as the video source, you might consider VGA to fibre optic converters. These will inherently eliminate any ground loops issues as well as give you extremely long video 'wire' run capability.

Greg
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Stu McDoniel

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Re: VGA HUM ELIMINATION
« Reply #6 on: August 09, 2011, 08:37:10 pm »

Is there a VGA HUM ELIMINATOR on the market?
What do you use to eliminate hum assosiated with VGA images?

Regards
Corne'
I experienced this on an LCD projector from a computer in one of my student computer labs.
This is simply "seeing" the ground loop in the video.  I simply use a ground lift on the projector
and the issued was resovled.
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Lee Buckalew

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Re: VGA HUM ELIMINATION
« Reply #7 on: August 09, 2011, 09:24:28 pm »

Quote
I experienced this on an LCD projector from a computer in one of my student computer labs.
This is simply "seeing" the ground loop in the video.  I simply use a ground lift on the projector
and the issued was resovled.

So you removed a safety ground from a piece of gear designed with a safety ground?
Really quite a bad idea (if thats what you meant).  You should instead isolate the video signal link.

Lee
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Brad Weber

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Re: VGA HUM ELIMINATION
« Reply #8 on: August 09, 2011, 09:52:40 pm »

I experienced this on an LCD projector from a computer in one of my student computer labs.
This is simply "seeing" the ground loop in the video.  I simply use a ground lift on the projector
and the issued was resovled.
As Lee noted, what do you mean by this?  If you mean that you used a device to lift the signal ground then I am curious as to what exactly you used.  If you mean that you used an adapter intended to provide a safety ground path by connecting the ground wire of the three prong device via tab or wire via a metal plate to a metallic conduit system but did not attach the tab or wire to provide that path, then while that may have helped identify the problem it is also unsafe and most likely a code violation, thus it should be removed as soon as possible.
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Tom Hester

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Re: VGA HUM ELIMINATION
« Reply #9 on: August 10, 2011, 01:59:57 am »

As Lee noted, what do you mean by this?  If you mean that you used a device to lift the signal ground then I am curious as to what exactly you used.  If you mean that you used an adapter intended to provide a safety ground path by connecting the ground wire of the three prong device via tab or wire via a metal plate to a metallic conduit system but did not attach the tab or wire to provide that path, then while that may have helped identify the problem it is also unsafe and most likely a code violation, thus it should be removed as soon as possible.

I pulled about 20 of these from an install. Every single piece of gear had one on it. Including the home depot power strips. Once I moved all of the audio gear onto the transformer, they were surprised at how quiet it was without the ground lifts.


If this is what you are talking about, please don't use these permanently. As I think Brad is pointing out.
« Last Edit: August 10, 2011, 02:03:01 am by Tom Hester »
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Re: VGA HUM ELIMINATION
« Reply #9 on: August 10, 2011, 01:59:57 am »


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