Jump to content

URGENT VGA/projector problems


Recommended Posts

I´m having a few problems and hoping someone can give me a little inspiration..

I have till tomorrow to fix this!!


I have a 12.000lumen sanyo projector hung on a truss with 180ish channels of dimmable lighting fixtures.

There is a VGA run to the control of 50mtrs

Directly from the computer there is a vga DA to feed projector and preview, then at around the 30mtr mark in the truss there is a 2nd VGA DA.


The control/opp area is connected to its own 3phase feed apart from the dimmers.. the projector and DA in the truss are connected to the sound feed.


I´m suffering BADLY from white horizontal scanning lines when any dimmer channels are dimmed... at 0 or 100% dimmers there is no noise in the signal...


The VGA line is taped to one tube of the (large) truss where NOTHING else is taped.. its on its own completely.


WE have tried all the naugty tricks of removing the earth from certain parts of the system to fault find, to no avail..



suggestions please??????!!!

Link to comment
Share on other sites

I've had similar issues on a RCA lead which ran behind an old TV. But I've never experienced it on a VGA before. What is the model of your projector? I know with some projectors you can send video over CAT5 or USB. Which if it comes to it and you have to get a new cable, could be easier to get access to. Could you try a direct VGA from the projector just hanging from the truss to a laptop/computer. and see if that works?
Link to comment
Share on other sites

No humbuckers, or any other such kit.. we´re a lighting company with MINIMAL video kit........ grrr



Just now we have tried removing the main 400A earth connector to see how it affects...


There is much less noise than before but still a litttle...


so an entire rig with no earth... "fun" :S

Link to comment
Share on other sites

Definitely sounds like an earthing issue... I'd be trying the PC VGA directly into projector, then with DA2 in circuit, then DA1... start with just the first 20m vga cable (and with a laptop running from battery)


I assume they're decent quality cables?


Is it possible to get the projector, both DAs and the PC on the same phase, fed from the same source?

Link to comment
Share on other sites

unfortunately the last VGA we have here, is broken


Truth is I cant vouch for the VGA cables as they are brand new... from a trusted supplier... but that isnt really saying there might not be problems with them!


Were wondering more also about the cables as we have just tried connecting the projector to a COMPLETELY separated supply from "backstage" and it still is suffering the problem..

The truth is that there is a tiny amount of hum in the sound system too... but its so low that I in most jobs you could "ignore it" as the sound level will just drown it out.. during hte day with carpenters and people working I didnt even notice it.. Just now at 1am, just 3 of use here focusing the lights can I hear it in the silence of the exhibition centre.


I´m adding a photo.. the red line shows where the cable currenltly is run.. as I said in one corner of hte truss, and it is the ONLY cable in that corner...

Tomorrow we are going to try just running a cable slap bang down the centre from cross brace to cross brace... and hang the "beauty of it", that way we can throw a cable, from the ground" over a brace... plug it into the laptop and test.. add the next cable, test and sling it over... and repeat.. (green line)




we also tried the projector on all 3 phases.. no change

Link to comment
Share on other sites

You might need to electrically isolate the projector from the truss. I have had situations where the metal clamps contacting the bar were proving a problem and making a huge ground loop.


As an example, you could wrap the truss in leccy tape under the projector clamps, or suspend the projector on a couple of spansets below the main truss?

Link to comment
Share on other sites

+1 to davids reply.


We had that on Beauty and the Beast where we were getting scanning lines. Projector was rigged on a FOH bar on a unicol bracket. For ease, we landed up putting a small piece of carpet between the top of the clamp and the scaff bar so it sat on the carpet. Worked a treat. -- We did the same things, power, different cables, but in the end, that is all that it was.

Link to comment
Share on other sites

Sorry for the no reply.. been a mental day..


In the end we´ve had earth problems left right and centre.. and after lunch we ended up stripping the entire rig into its component parts, dissconnecting them from the supply one by one looking for the fault


In the end... The sound had 2 bad XLRs in the multicores up in the truss...

The projector, you guys were SPOT ON, I isolated the entire rig with LX tape at the projector, DA in the truss and all the metal female-female joins.


we still have problems in the plasmas disribuited around the building but even the client has gotten to the "sod it stage".


its amazing how the BR can give you the clarity of mind you dont have after a 2 week rig of 14 hour days!!!


Tomorrow. models.. and lots of them :blink:

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.