TV Monitor Display Issue AND now projector problem.

[moosicman]

Hey folks! We just put three plasma TV monitors up to display announcments and services in different areas of our facility and two issues have popped up that I'm clueless to sort out.

One is that the image on 2 of the 3 TVs is shifted to the right or left with the ole black bar on one side. This happens intermittently and on one of these, sometimes it is just that the image is squeezed but all on screen while the other actually loses part of the image. Sometimes when you turn on the TV it will be full screen as it should be and sometimes it will come on full for a moment and then "pop" to the off-center position. It doesn't appear to be a ratio setting as they only have two settings and we've toggled both with even worse results (4:3 and 16:9).

I suspect it has something to do with how we are sending signal to it, which is probably causing my second issue (addressed after brief explaination). We are sending a PP4 MAC Extended Desktop image out to a distribution amp with several outs (which PRE-TV installation, two went directly to our forward and backward projector in sanctuary). We used a distribution splitter out of one of these to send signal to one of the TV's and then to the back projector, which has caused the back projector to display everything in Frankenstien green (my second issue).

I'm not presently at the church so I can't give you models of dist. amps and I can't remember if we're coming out of the amps other sends going directly to the other 2 TV's or if we are somehow splitting and going to them as well but I know that ONE of them is full screen and the others have been at one time or the other, but at completely random times.

Any thoughts?

[moosicman]

Oh, and I'm pretty sure we're breaking some rules that we should be following about splitting signal or something along these lines. I'm good when it comes to sound but not so saavy in the A/V dept. about signal loss and do's and don'ts. We had a contractor who has installed media before and who seems to know what he is doing but once I get to the church and tell you the exact signal routing I'm betting you'll tell me that I can't do that and need to do "X".

[Brad Weber]

It could be at least partially related to the signal distribution and it would help there to know as much as possible about the actual distribution devices, cable run lengths, signal type being distributed, cable used, etc.

Another potential factor is the signal itself. One of the common issues when distributing a computer signal to multiple displays is having a signal resolution and scan rate that all of the displays support. This may mean getting out the manuals for each device and finding a resolution and scan rate that they supposedly all support and then configuring the computer to provide that signal. This can be especially applicable to "video" versus "computer" displays and devices as they may only accept standard "video" resolutions and scan rates or maybe those along with just a couple of basic computer resolutions.

[sempei13]

I'd spend some time troubleshooting. First thing, if you swap the DA out between two tv's (one good and one w/ trouble) does the problem follow the tv or the DA channel.

If it follows the tv (and the wiring from the DA to the tv), I'd try and remove as much as possible and try and get a straight feed from the computer to the tv. If the problem goes away, it could be cable run or one of the pieces you removed. If it doesn't, check resolution.

You could also swap tv locations and see if the problem follows the tv or the location. If tv, check resolution. If location, check cabling, etc.

Paul

[D.R.HADDOCK]

The shifting of an image to the side, means incorrect line lock,
That means the sync signals are being degraded somewhere,
Because the horizontal sync signal is the highest in frequency
then it is the first to suffer, which is why the picture is shifting to the side.
Somethings to check - Are the cables good quality and correct impedance ?,
Are the cables too long ?
Even with the best quality cable there is a limit to lengths.
Are all equipment in the video chain correcttly impedance matched ?.
Standing waves can be a problem in big distro systems.
Which is why professionals spend big bucks on expensive video
distribution equipment.
You might have to consider using cat 5 for distro,
it seems to be less probromatic on long runs.

[moosicman]

Thanks for the pointers. Thus far we've solved some of the issues. However, we still have one TV with an image shift to the right. All others are centered. It's like someone clicked the "arraign right" button.

Here is what I've done to track it down that didn't work. I've taken the input cable to that one TV (bypassed everything entirely) and connected it immediately out of the back of the FSR CO-2001 Compass Presentation Switcher output. The connections are VGA that our installer wired together. I've compared his wiring of the top (RGBHV) to the other TV cables and they all look to be the same (blue where blue goes, red where red goes, etc.) and thus correct. The wires from the bottom of the VGA connector do go into different places on the 2 TVs that work. The one that doesn't work looks like one of the ones that DOES work. I don't know what is correct. ARGGGGG THIS ONE TV!!!!! The cable isn't a long run at all, in fact it is the shortest one. Oh, it is all CAT6 cable being wired with VGA connections. Any suggestions.....*whimper*

[moosicman]

Please note that I do not mean a shadowing of the image on the TV (though we do have that issue as well - a shadowing of the image about 1-2 inches to the right but it is bearable for now as it is not really too noticeable). I mean that the entire picture display is shifted, with the right 6 inches chopped off the TV.

[D.R.HADDOCK]

Originally Posted by moosicman

Please note that I do not mean a shadowing of the image on the TV (though we do have that issue as well - a shadowing of the image about 1-2 inches to the right but it is bearable for now as it is not really too noticeable). I mean that the entire picture display is shifted, with the right 6 inches chopped off the TV.

If there is a shadow image present in any form,
This means there are standing waves present !
This is most likely caused by an incorrect impedance,
possibly a wrong type of cable.
This would also upset the sync signals,
hense the wrong line lock (shifted pic).
Check for correct impedance on everything,
and check the impedance of all the cables.

[Paris MkVI]

Hear, hear what "the Doctor" has written above.

Based on what I am reading, your installer has done you a disservice, with incorrect impedance, cabling and connections.

Did I read right, Cat 6 cable used with either VGA or RGBHV BNC connectors? Not VGA-to-baluns converting the signal to distribute over CAT 5 or CAT 6?

Really?



See this old, but still useful thread about VGS over CAT 5.