Squiggly Lines On My Projector

[BackstageAlex]

Our projector has started showing squiggly lines across it when it is displaying text. It's not really noticeable on graphics/video, or from a distance, but from the first couple of rows of our auditorium it's very prominent when showing white text. Anyone have any ideas? We run it from our computer to an extron scaler and then through a crestron switcher.

[mnfreelancer]

How long is the cable run? What type of cable - D-sub [vga] or RGB-HV [5-wire]?

[BackstageAlex]

It's about 100ft all together, but it hits an amplifier at around 50 ft.

[JohnHartman]

Are the squiggly lines running vertically or horizontally?

Have you tried bypassing the various pieces of hardware to see if you have a issue in your signal chain or with a cable rather than an issue with the projector.

You can also try adjusting the clock or fine sync to adjust the waver out of the image if you have access to that setting.

[tjrobb]

One other thing I might add is ground loops. If the various items have differing resistances to ground the signal can get out of sync (see previous posts). The best way around this is a ground lift, or opto-isolation if possible.
I might add that I don't do many installs, so take this with a grain of salt.

[museav]

You mentioned that it "started" doing this, so the same system was not doing it before? If so, that seems to suggest something that changed. That could commonly be the computer used as a source or its video settings. Or someone could have possibly adjusted or changed some setting in the Extron scaler. Or some setting drifted, such as clock or phase for the projector.

It seems to be often overlooked that distance issues with video, and especially "VGA" signals, relate to both the length of the run and the bandwidth of the signal, which is greatly resolution dependent. A setup that works fine for 1024x768 may exhibit problems with 1600x1200 signals even though both use the same connector and cabling. I don't know if this is applicable to this particular situation but I have encountered situations where people assumed that higher resolution was always better or that upgraded projectors and then wondered why these "improvements" looked worse.