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Second monitor stopped working in correct resolution

Brief issue description:

Laptop stopped recognizing second monitor properly. Works in 1024x768 instead of 1680x1050 now. Higher resolutions miss from settings. NOT a new monitor, worked with this laptop just fine before. How to fix?

More details:

I have a Lenovo ThinkPad T400 laptop with Fedora 22 (KDE spin) and kernel-4.2.8-200 on board with dual monitors. One is its own LCD (1440x900), the other one is Samsung SyncMaster 2043NW (1680x1050), hooked up to a VGA port. It all has operated just fine until earlier today.

I was using it dual monitor this morning, then detached the second monitor and took the laptop with me to surf the web on couch for a couple hours (and that's exactly what I consequently did, I didn't install or remove anything), then I reattached it, and boom! No more 16:10 second display, its video output is 4:3 now, 1024x768, vertically stretched, with black stripes on the sides. I can't set it to any resolution higher than that. Any ideas how to make it work in 1680x1050 again?

What I've already done:

1. Rebooted several times, detaching the monitor and reattaching it before, during and after the reboot. No luck.
2. Tried every possible combination of settings in Display Configuration (not like there were a lot of, though). No luck.
3. Updated the system (as that sometimes solved the minor issues, priorly appearing out of nowhere). No luck.
4. Tried to Google. No luck: machine of literally every other similar thread's OP fails to recognize his second monitor right from the start, while mine did it just fine not half a day ago!
5. Performed several tests, results are in the section below.

Additional facts to help with diagnosing the issue:

• The second monitor fell off the platform it stands on a day ago, detaching from the power cord, but not from the VGA. But when I plugged the power back in, it continued to work properly. The moment when the laptop stopped recognizing it may be the first time I detached it ever since. I don't exactly remember.
• In System Settings —> Display and Monitor —> Display Configuration it used to show up as Samsung SyncMaster, or something of a kind. Now it shows up as VGA1.
• Live versions of Fedora 22-3, OpenSUSE Leap 42.1, Ubuntu 14.0.3 LTS and Arch Linux 2016.01.01 now all recognize my second monitor the same way (1024x768, don't detect the model). May not be the clue as I don't remember running any Live versions dual monitor ever before, so I don't know, how should they behave on this H/W.
• Windows 8.1 recognizes it properly as a secondary monitor right away (tested with my GF's laptop).
• As a primary one, though, Windows 8.1 at first failed to recognize it, but then I restored factory settings of the monitor and it started being recognized properly (tested with my desktop PC with nVidia GTX 550 Ti on ...
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2 Answers

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Nevermind, rebooting the laptop once again after resetting my monitor to the factory settings did the trick. But I don't close the topic, as I'm still curious, how can I force a resolution, which is not on the list (as I might have needed it if rebooting was to fail).

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Since the original problem has been solved by rebooting onto your question of how to force resolution...

You could try to create a mode line with cvt tool with following syntax:

cvt widthinpx heightinpx refreshrate


example:

cvt 1920 1080 60
xrandr --newmode "1920x1080_60.00"  173.00  1920 2048 2248 2576  1080 1083 1088 1120 -hsync +vsync
xrandr --addmode VGA-0 1920x1080_60.00

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Asked: 2016-01-22 19:19:07 -0500

Seen: 1,075 times

Last updated: Jan 26 '16