我已通过 VGA 连接了第二个屏幕，但没有信号（第二个屏幕是黑色的）。我尝试过更改第二个屏幕的分辨率、重新启动等，但到目前为止没有任何效果。帮忙吗？
这是 xrandr 的输出：
Screen 0: minimum 320 x 200, current 2752 x 900, maximum 16384 x 16384
LVDS-1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 345mm x 194mm
1600x900 59.99*+ 59.99 59.94 59.95 59.82 50.00
1440x900 59.89
1400x900 59.96 59.88
1440x810 60.00 59.97
1368x768 59.88 59.85
1360x768 59.80 59.96
1280x800 59.99 59.97 59.81 59.91
1152x864 60.00
1280x720 60.00 59.99 59.86 59.74
1024x768 60.04 60.00
960x720 60.00
928x696 60.05
896x672 60.01
1024x576 59.95 59.96 59.90 59.82
960x600 59.93 60.00
960x540 59.96 59.99 59.63 59.82
800x600 60.00 60.32 56.25
840x525 60.01 59.88
864x486 59.92 59.57
800x512 60.17
700x525 59.98
800x450 59.95 59.82
640x512 60.02
720x450 59.89
700x450 59.96 59.88
640x480 60.00 59.94
720x405 59.51 58.99
684x384 59.88 59.85
680x384 59.80 59.96
640x400 59.88 59.98
576x432 60.06
640x360 59.86 59.83 59.84 59.32
512x384 60.00
512x288 60.00 59.92
480x270 59.63 59.82
400x300 60.32 56.34
432x243 59.92 59.57
320x240 60.05
360x202 59.51 59.13
320x180 59.84 59.32
VGA-1 connected 1152x864+1600+0 (normal left inverted right x axis y axis) 477mm x 268mm
1920x1080 60.00 +
1600x1200 60.00
1680x1050 59.95
1280x1024 75.02 60.02
1440x900 74.98 59.89
1280x960 60.00
1280x800 59.81
1152x864 75.00*
1024x768 75.03 70.07 60.00
832x624 74.55
800x600 72.19 75.00 60.32 56.25
640x480 75.00 72.81 66.67 59.94
720x400 70.08
其他信息：
- 显卡：英特尔® 高清显卡 4000 (IVB GT2)
- 操作系统名称：Ubuntu 20.04.3 LTS，64 位，3.36.8，X11
谢谢！！