image shift VGA

[sarahsliefie]

We have a Projector system with 3 projectors all showing duplicated images form a powered VGA matrix. When I run them from the booth no problem at all, but when I run them from the stage the image shifts about 1/10 to the left. The stage is 100' further away so I thought it was a loss of signal. When a connected an amplifier there was no change. All cables are high quality and the only main differences it is it a different input on the Matrix. It is about 100' further. And we are using a laptop not the projection computer in the booth. I have tried switching the matrix inputs and that did not fix it. The only thing that I have not tried is changing the computer. it there anything else I should try? is there anything I am missing?

 

[ruinexplorer]

What is the distance from the laptop to the matrix? A laptop does not have as strong of an output as a desktop and thus has a shorter range for analog signals (I generally stay within 50' for an unamplified laptop signal as results over that may vary). What is the model of the matrix? Just want to make sure we are on the same page.

 

[sarahsliefie]

It is just over 100' from the laptop to the matrix. the matrix is a Gefen EXT-VGAAUD-444 4x4 VGA Matrix. I tried putting an amplifier in line and did not get any change in the signal. This is the amplifier we used. Amazon.com: C2G / Cables to Go Trulink VGA Video Extender 1PORT M/f: Electronics
Would signal loss cause the whole picture to shift and leave me with a black bar down the right side?

 

[Chris15]

What is the cable to stage?

Sounds to me like you have a skew issues on the H sync line...

 

[museav]

The shift is almost certainly a timing or sync rather than level issue. And there is probably some simple troubleshooting to try before starting to replace hardware.

The Gefen VGA matrix does not provide EDID information to the laptop so it should not matter but have you tried having the laptop hooked up to the matrix switcher and projectors turned on before booting up the laptop? And since no EDID information is provided, have you tried changing the laptop video output settings or verifying that the settings are compatible with the projectors, perhaps something like the native resolution of the projectors with a refresh of 60Hz or something common?

Have you tried connecting the laptop direct to the matrix switcher to eliminate the long cable run from the stage? Or connecting a monitor or other display direct to a matrix switcher output to eliminate the projector and that associated cable run?

 

[StNic54]

If you truly had signal loss, I think you would see more sync and color issues, not a lens/image shift. We run video well over 100' every show with never an issue like that. I'd say its in your switcher settings with your laptop. If you have extra cable, try running a separate cable to make sure it's not your distance, but my money is on your input settings on your switcher. Also make sure you save your settings as you go and always double check it before house opens each time. Remember your laptop output settings are very different than a pc video card, so you'll find yourself adjusting your switcher settings to compensate. Try a different computer, try the different inputs for the pc, and that should clarify what you are seeing.

 

[sarahsliefie]

I tried a different computer and got the same thing.
So I brought the laptop up tot he booth and plugged it into the matrix with a 12' cable. It worked great.
I tracked the cable and it goes about 50' to a junction. I plugged in the lap top there and it worked great.
I tracked the cord from there and it winds in an odd direction. come to find out the second cord is about 125' more for a total distance of 175'
At the end of the whole 175' I get the shift in image. I change the picture quality and at the lowest setting the shift is not as bad but it is still unacceptable.

this leads me to two other questions.
1. How can I amplify the signal to make the whole distance, and where should the booster be placed.
2. Do you guys know what signal booster I should use. The one I have does not work.

My long term goal would be to string cat6 and do a VGA over that. But I can not get that done in the next week.
any other suggestions you have would be great.

 

[museav]

If the horizontal shift is the only problem and you are not experiencing smearing, fuzzy or faded images, the projectors having trouble syncing in general, etc. then the problem may be related to the sync timing and amplifying the signal may not solve it. Something like VA-1H - Video/Computer/Sync Processors - Kramer Electronics or Extron Sync Processors - SCS 300 could be used to correct the sync signal. These are usually most effective when located at the end of the run, which would typically be at the display, but with your matrix switcher and the intermediate connection it might be best to locate it at either the matrix switcher input or since the intermediate junction point directly does not experience the problem, at that point to compensate for the long initial run.