One Slackware system I have has three NEC EX231w monitors. One of the monitors is intermittently recognized. I have ruled out cables and the graphics card. Apparently the monitor does not recognize all the time that it has a signal. It may work for 3 minutes, and then not for a couple of hours. Tapping the monitor does not help. Temperature does not seem to help.

Probably my next step will be to open the monitor up, and look on the input side of the processor for cold solder joints.

Anyone have any other ideas?

Unplug power cable and wait a few seconds then plug back in. Does it fix it?

No and moving around the three power supplies doesn't help either.

What if you switch the order of the monitor connections?

I have switched the cable ordering, and the monitor behaves the same.

NEW observation. I have been reconfiguring hardware, and rebooting allot.

The monitor work OK 95% of the time on a boot. After KDE is started, the monitor blanks out after one or two seconds, or sometimes stays up for minutes. It is always the same physical monitor that blanks out, even though the cables are getting swapped.

If I reboot, the monitor usually comes to life. So something from KDE running is causing it to blank, most of the time. If I boot off a live disk, and don'[t juggle the monitors (all show the same screen) the monitor stays lit for sometimes hours.

Any ideas on how to isolate things further?