Video resolution, and a problem with LG display

I have an Precis LT 4x4 VGA switcher - the first I've bought since AMX took them over - and it acts different than previous versions of the switch. The Autopatch appears to always advertise the highest resolution possible for it. Whenever I plug a computer's VGA output into it, the computer always adjusts to a resolution that virtually no display or video output device can handle.

To be able to get viewable video from a Mac through the Autopatch, I had to put a simple VGA splitter between the computer and the autopatch, and plug a monitor into the VGA splitter. Then the Mac would read the display's resolutions and output a reasonable 1280x1024 signal and that signal will go through the autopatch to it's destinations just fine. If I remove the VGA splitter, poof! there goes my video signal.

Is there a way to force the Autopatch to advertise a specific resolution like 1024x768 as a default?

Also, with this same switch, I ran into a problem with an LG display. If the VGA cable was connected between the Autopach and the display, the AMX controller would not power up the display. If the display was already powered up, the serial controls would work fine, including power-down. But then it would not power up via serial control. The serial port on the LG display just went dead.

We had to disconnect all pins on the VGA cable except for the R, G, B, Synch, and Synch ground lines to get the serial port to act on a power-up command when powered down. It was one of the 3 RGB ground wires that appeared to be causing the problem. I'd never seen this problem before. Has anyone else ever seen anything like this?


  • DHawthorneDHawthorne Junior Member Posts: 4,584
    Gefen makes a little box that can learn the EDID from your monitor so that whenever the computer queries the monitor for its resolution capability, the box reports back instead, and you get the resolution your monitor can handle, not what comes out of the switch. It's also good for forcing a computer to the "lowest common denominator" when it needs to switch between various monitors. And it can store DVI and HDCP settings so you don't lose your picture if the source device resets and the "wrong" monitor is on at the time. I've used them with great success for computer video switching applications. Find it at: .
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