Previously worked perfectly with the following:
Desktop (Windows 7) connected to monitor with original DVI cable supplied with monitor
Dell Inspiron 5547 (Windows 8.1) laptop with an HDMI output connected to monitor via an HDMI to DVI adapter that I purchased from Dell.
Both computers worked with the VGA cable that came with the monitor. Now VGA is intermittent. I've tested the cable with another computer and there is no problem.
NOTE: I've never had the monitor connected to 2 computers while they were turned on or while the monitor was turned on.
Now the monitor does not work with DVI -- no video display. The laptop can't detect the monitor under Control Panel > Display > Screen Resolution. It only detects the built-in monitor. I can't check this on the desktop because there's no video display.
I also bought a display port > HDMI adapter, but read some posts explaining the need for a converter, so I will ignore for now that it doesn't work with DP since I may have the wrong adapter.
I've followed the reset instructions and the onscreen diagnostics, which doesn't make any difference. The problem is no display at all, not just a bad display.
Is it still Dell's policy not to repair out-of-warranty monitors? I purchased the monitor directly from Dell and I find it rather hard to believe that there is no way to repair a $300 monitor that is only 3 years old.
Any suggestions would be welcome. Or am I out of luck and have to buy a new monitor?