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Author Topic: signal loss to projector  (Read 2231 times)

Bill Beach

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signal loss to projector
« on: February 25, 2016, 11:17:10 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. 
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 the signal is VGA.
right after the VP-719DS in the video projection booth is a 1x5 VGA distribution Amp.  one output on this unit goes to the video recording booth upstairs (there converted to composite video to mix in with video from 2 cameras).  another output goes to the projector for the back wall, and then 2 outputs going to the overflow area projectors on the right and left sides.  the 2 overflow and the back projector have VGA from the booth to each projector.  then the signal to the front area is converted to HDMI then sent to the front via Cat-6 for the 120 foot travel and back to HDMI & then goes through a 1x2 Kramer HDMI Distribution Amp.  this feeds 2 projectors, one for each side of the front area, above the stage.
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 then reappear in about the same time it takes to read this.  we don't see it 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 projectors.
we notice this on the back and the front 2 projectors.  some times simultaneously and some times individually.  even though the front 2 projectors get the same single HDMI via Cat-6, some times only one will go blank.  and which one is variable and random.
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.
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David Buckley

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Re: signal loss to projector
« Reply #1 on: February 26, 2016, 06:49:34 am »

So let me get this straight; you get occasional dropouts on a projector that is fed with VGA ("back"), and also on projectors ("from left and right") fed by a common HDMI link?

Do the video guys upstairs ever complain of dropouts?
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Bill Beach

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Re: signal loss to projector
« Reply #2 on: February 29, 2016, 10:56:04 pm »

So let me get this straight; you get occasional dropouts on a projector that is fed with VGA ("back"), and also on projectors ("from left and right") fed by a common HDMI link?

Do the video guys upstairs ever complain of dropouts?
short answer = yes and no
not sure if our setup is different or similar to others, but we actually have just one video guy upstairs doing the camera work and 'editing' on the fly.  no problems reported.

the common denominator for the front 2 and the back projector is that they all come from the Kramer VP-719DS presenter.  this unit outputs a VGA signal that goes into a splitter.  from the splitter, the signal for the front 2 projectors is converted to HDMI then ran through Cat-6 to the front.

this weeks services, we didn't see any drop outs.  whassup wit dat?!?
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John Rutirasiri

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Re: signal loss to projector
« Reply #3 on: March 03, 2016, 04:18:37 am »

I'm not sure if this has anything to do with signal loss (unless the VGA DA is defective).  I'm suspecting you're seeing issues with EDID when you switch sources.  The VGA distribution amplifier (most) do not have any facility to maintain EDID to the outputs, and simply pass through the EDID.  When you switch sources, the EDID is resent and hence the temporary blank.

You can buy VGA EDID emulators for fairly cheap which should take care of this issue.

The better HDMI splitters have EDID management so this is not an issue.

John R.
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ClearImpact Sound & Event Services, Inc.
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Cailen Waddell

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Re: signal loss to projector
« Reply #4 on: March 03, 2016, 08:12:49 am »


I'm not sure if this has anything to do with signal loss (unless the VGA DA is defective).  I'm suspecting you're seeing issues with EDID when you switch sources.  The VGA distribution amplifier (most) do not have any facility to maintain EDID to the outputs, and simply pass through the EDID.  When you switch sources, the EDID is resent and hence the temporary blank.

You can buy VGA EDID emulators for fairly cheap which should take care of this issue.

The better HDMI splitters have EDID management so this is not an issue.

John R.

+1. I have found Kramer gear in particular to be especially crappy at passing edid correctly....  What finally increased reliability for us was edid emulators on every VGA input.

I'm assuming you VGA splitter is in fact at powered DA not a passive splitter?

Also - you seem to be doing a whole lot of converting....  That just creates sources for issues.  When an HDMI signal is lost even for a very short moment, resync takes a lot longer than VGA typically does.  I have not found anything but HD-base-t converters to be reliable for transporting HDMI over cat 5... 

I'd start at one end, maybe the projector end and remove problems one at a time.  Does an HDMI monitor at the pj show the issue?  If so move the monitor to right after the HDMI VGA conversion,   If so move back to before the converter with a VGA monitor and so on....

And the following I say with lots of experience and a little less hair from pulling it out.  Just because you can convert your video signal to different standard and utilize existing parts doesn't mean you should.


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Cailen Waddell

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Re: signal loss to projector
« Reply #5 on: March 03, 2016, 08:14:31 am »

Also are you using shielded cat 5e or cat 6?   I have had rf issues with non HD base t transport of HDMI over Ethernet cable.


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