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Author Topic: signal loss to projector  (Read 4554 times)

Bill Beach

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signal loss to projector
« on: April 16, 2011, 03:49:23 pm »

we have a relatively small church and we use video projection for the words to songs and sermon notes, etc.  we have a main seating area and two additional seating areas on left and right side of the main area.  we have a projector in each of the seating areas as well as one on the back wall as a confidence monitor for singers on stage. 
our system grew from a single projector to what we now have in small incremental steps.  for that reason the current setup is somewhat convoluted.  from the projection booth in the back of the main seating area, the signal is run through a Kramer VP-719DS switcher.  the signal from the computer to the VP-719DS is DVI.  from the VP-719DS everything is VGA.
right after the VP-719DS in the video projection booth is a Cables-to-Go 1x2 VGA distribution Amp.  the thru output on this unit goes to the video recording booth upstairs (there converted to composite video to mix in with video from 2 cameras.  one output goes to the projector for the back wall, and the other output goes to a point on the right side near the front (original position of the computer for video projection).
the signal to the front area is converted to Cat-5 for the 100 foot travel and back to VGA & then goes through a Cables-to-Go 1x4 VGA Distribution Amp.  three of these outputs feed the projectors for each of the seating areas.  the right overflow seating area has about 35 feet, the main projector has about 75 feet, and the left overflow seating area has about 120 feet of travel; all on VGA cable.
now the problem.................
every now & then and totally random (as far as we can tell) one or more of the projectors will go blank and show a message that it can't find a signal.  that will last for a few seconds then the projected image will re-appear and the projector will show a message that it now has a VGA signal on port 1 for computer input.  sometimes we won't see it for an entire service, but other times it may be 10-15 times in an hour (or so) service.  we don't see it too often on the projectors in the overflow areas because as soon as the preacher starts the sermon, we switch to the video camera feed (so overflow people can see the Pastor).  that is a whole different line and input for the projector.
early on we were only noticing this on the main projector and sent it in for warranty service twice.  they couldn't find anything wrong, but replaced related circuit boards anyway (twice).  now we notice this on the back and the front projector.  some times simultaneously and some times individually.
now the question...................
if we were to go to a 1x4 VGA to Cat-5 Converter / Distribution Amp, and run all lines as Cat-5 to each projector then convert back to VGA for the projector; does it appear this will help with the 'signal loss' situation?  (clean up the signal path, as it were)
I realize this is long, but wanted to try to give enough info to make a determination.  however, if there is more info needed, let me know and I will do my best to provide it.
« Last Edit: June 04, 2011, 12:57:11 pm by Bill Beach »
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Lee Buckalew

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Re: signal loss to projector
« Reply #1 on: April 17, 2011, 08:01:46 am »

we have a relatively small church and we use video projection for the words to songs and sermon notes, etc.  we have a main seating area and two additional seating areas on left and right side of the main area.  we have a projector in each of the seating areas as well as one o9n the back wall as a confidence monitor for singers on stage. 
our system grew from a single projector to what we now have in small incremental steps.  for that reason the current setup is somewhat convoluted.  from the projection booth in the back of the main seating area, the signal is run through a Kramer VP-719DS switcher.  the signal from the computer to the VP-719DS is DVI.  from the VP-719DS everything is VGA.
right after the VP-719DS in the video projection booth is a Cables-to-Go 1x2 VGA distribution Amp.  the thru output on this unit goes to the video recording booth upstairs (there converted to composite video to mix in with video from 2 cameras.  one output goes to the projector for the back wall, and the other output goes to a point on the right side near the front (original position of the computer for video projection).
the signal to the front area is converted to Cat-5 for the 100 foot travel and back to VGA & then goes through a Cables-to-Go 1x4 VGA Distribution Amp.  three of these outputs feed the projectors for each of the seating areas.  the right overflow seating area has about 35 feet, the main projector has about 75 feet, and the left overflow seating area has about 120 feet of travel; all on VGA cable.
now the problem.................
every now & then and totally random (as far as we can tell) one or more of the projectors will go blank and show a message that it can't find a signal.  that will last for a few seconds then the projected image will re-appear and the projector will show a message that it now has a VGA signal on port 1 for computer input.  sometimes we won't see it for an entire service, but other times it may be 10-15 times in an hour (or so) service.  we don't see it too often on the projectors in the overflow areas because as soon as the preacher starts the sermon, we switch to the video camera feed (so overflow people can see the Pastor).  that is a whole different line and input for the projector.
early on we were only noticing this on the main projector and sent it in for warranty service twice.  they couldn't find anything wrong, but replaced related circuit boards anyway (twice).  now we notice this on the back and the front projector.  some times simultaneously and some times individually.
now the question...................
if we were to go to a 1x4 VGA to Cat-5 Converter / Distribution Amp, and run all lines as Cat-5 to each projector then convert back to VGA for the projector; does it appear this will help with the 'signal loss' situation?  (clean up the signal path, as it were)
I realize this is long, but wanted to try to give enough info to make a determination.  however, if there is more info needed, let me know and I will do my best to provide it.

You need to determine what is causing the drop out rather than just start replacing parts.  Get/borrow (or hire someone) a video signal test generator.  Test each cable run (each line of each run, including sync) without any interface devices except those required for CAT5 to VGA conversion.  This should tell you if you have loss and what it is through each line.
I have found that CAT5 adapters are often the problem.  First, I have not come across any inexpensive ones that actually look as good as a VGA signal run a few hundred feet.  Second, I frequently find nicked wires in the CAT5 where the outer cable jacket was stripped back.  Third, I often find the wrong CAT5 connectors used.  Either 110 punch are used without the correct tool or the correct prep or the cable mount ends are wrong (they are often ends for stranded wire mounted to solid wire or the other way around). 
As far as 110 punch, they can certainly be terminated with tools other than a punch down tool but, often I see them terminated in a way that over stresses the contacts so they don't have the "spring" to them that they should.

After testing the cables add your next layer of splitting/buffering and test from input to output again, keep adding and you should find the actual problem and be able to replace it.  If it's not a level issue then, you may have an intermittent connection problem that will take a bit more time to find.

Lee Buckalew
Pro Sound Advice, Inc.
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Lee Buckalew
Pro Sound Advice, Inc.
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