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#1 2016-06-13 12:13:36

asoundmove
Member
Registered: 2016-03-16
Posts: 5

[Solved] - External monitor randomly blanks frequently, stays blank

I have seen many reports of screens going randomly blank but none similar to what I experience.
After having worked perfectly for years on another (Ubuntu) laptop and for days on this laptop, the external monitor (VGA, LG Flatron L1915S) on my laptop now goes blank randomly and stays blank - even though the status LED on the monitor shows it is on.
I would love some help to diagnose and fix this issue.

I can't see any error message in dmesg.
Where the mouse is located in all of this (on which screen) seems to have no impact.

I can easily restore the screen by pressing the on/off button twice, or via software by running the following two commands (just issuing the second command does nothing):

xset dpms force suspend # or standby or off (same result)
xset dpms force on

But then the external monitor goes blank again, sometimes in less than one second, other times after several minutes, rarely more than half an hour. It does not seem related to the screen saver or DPMS, as it sometimes happens (after reboot) long before any DPMS or screen saver timeout is triggered (the laptop screen stays on).

I tried changing the refresh rate from the default 60.02 to the alternative 75.02, and it seemed to do the trick for the rest of one evening (even with a screen saver on), but the next day the blanking problem came back again.

I tried to disable blanking, it did not change anything, the screen still blanks after minutes or seconds

xset s noblank

If I reboot while the external monitor is blank, the reboot unblanks it.
I log in and let it sit for a while having started no application, blanking tends to not happen, though it sometimes does.
Sometimes it seems related to actions (closing a window on that screen, cursor leaving the window), other times it is clearly unrelated as some blanks happen when there is no on going action (mouse & keyboard untouched).
When the external monitor does go to stand-by mode after the relevant timeouts (and the main laptop screen is in stand-by too), shaking the mouse unblanks both monitors, but then the external monitor often blanks shortly afterwards.

Changing the refresh rate while the screen is blank does not unblank the monitor.

xrandr --output VGA-0 --rate 60.02
xrandr --output VGA-0 --rate 75.02

While issuing the command with the --mode switch does unblank the screen (although only momentarilly).

xrandr --output VGA-0 --mode 1280x1024 --rate 60.02
xrandr --output VGA-0 --mode 1280x1024 --rate 75.02

After one of many reboots the external monitor blanked before I could even login. I decided to login blind (with screen blank), when it opened the session, the screen un blanked, but then blanked shortly after again.

Trying to disable DPMS on the external monitor does not solve the problem:

> cat /etc/X11/xorg.conf.d/10-monitor.conf 
Section "Monitor"
    Identifier "LVDS"
    Option "DPMS" "true"
    Option "Primary" "true"
EndSection

Section "Monitor"
    Identifier "VGA-0"
    Option "DPMS" "false"
    Option "RightOf" "LVDS"
EndSection

Section "ServerLayout"
    Identifier "ServerLayout0"
    Option "StandbyTime" "0"
    Option "SuspendTime" "0"
    Option "OffTime"     "0"
    Option "BlankTime"   "0"
EndSection

> reboot

Some system information:

  • the laptop is an ASUS Pentium 4 with 1GB RAM, other than that recent screen blanking issue with the external monitor, everything works fine (a bit slow but fine).

  • I run lxde/lxdm with xscreensaver

> uname -a
Linux asm 4.5.4-1-ARCH #1 SMP PREEMPT Wed May 11 22:42:28 CEST 2016 i686 GNU/Linux

> lspci -v # video card:
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] RV200/M7 [Mobility Radeon 7500] (prog-if 00 [VGA controller])
        Subsystem: ASUSTeK Computer Inc. Mobility Radeon M7 (L3C/S)
        Flags: bus master, stepping, 66MHz, medium devsel, latency 64, IRQ 5
        Memory at d8000000 (32-bit, prefetchable) [size=128M]
        I/O ports at d800 [size=256]
        Memory at d7000000 (32-bit, non-prefetchable) [size=64K]
        Expansion ROM at d7fe0000 [disabled] [size=128K]
        Capabilities: [58] AGP version 2.0
        Capabilities: [50] Power Management version 2
        Kernel driver in use: radeon
        Kernel modules: radeon

> xrandr
Screen 0: minimum 320 x 200, current 2680 x 1050, maximum 4096 x 4096
VGA-0 connected primary 1280x1024+1400+0 (normal left inverted right x axis y axis) 376mm x 301mm
   1280x1024     60.02 +  75.02* 
   1152x864      75.00  
   1024x768      75.08    75.03    60.00  
   832x624       74.55  
   800x600       75.00    60.32  
   640x480       75.00    60.00  
   720x400       70.08  
LVDS connected 1400x1050+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1400x1050     60.77*+
   1280x1024     59.89  
   1280x960      59.94  
   1280x854      59.89  
   1280x800      59.81  
   1280x720      59.86  
   1152x768      59.78  
   1024x768      59.92  
   800x600       59.86  
   848x480       59.66  
   720x480       59.71  
   640x480       59.38  
S-video disconnected (normal left inverted right x axis y axis)

> xset q
Keyboard Control:
  auto repeat:  on    key click percent:  0    LED mask:  00000000
  XKB indicators:
    00: Caps Lock:   off    01: Num Lock:    off    02: Scroll Lock: off
    03: Compose:     off    04: Kana:        off    05: Sleep:       off
    06: Suspend:     off    07: Mute:        off    08: Misc:        off
    09: Mail:        off    10: Charging:    off    11: Shift Lock:  off
    12: Group 2:     off    13: Mouse Keys:  off
  auto repeat delay:  500    repeat rate:  33
  auto repeating keys:  00ffffffdffffbbf
                        fadfffefffedffff
                        9fffffffffffffff
                        fff7ffffffffffff
  bell percent:  50    bell pitch:  400    bell duration:  100
Pointer Control:
  acceleration:  20/10    threshold:  10
Screen Saver:
  prefer blanking:  yes    allow exposures:  yes
  timeout:  0    cycle:  0
Colors:
  default colormap:  0x20    BlackPixel:  0x0    WhitePixel:  0xffffff
Font Path:
  /usr/share/fonts/misc/,/usr/share/fonts/TTF/,/usr/share/fonts/OTF/,/usr/share/fonts/Type1/,built-ins
DPMS (Energy Star):
  Standby: 7200    Suspend: 7200    Off: 14400
  DPMS is Enabled
  Monitor is On

Last edited by asoundmove (2016-06-14 07:42:28)

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#2 2016-06-13 14:43:26

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 19,739

Re: [Solved] - External monitor randomly blanks frequently, stays blank

That is an LCD display.  You also say that it is years old; perhaps old enough to use CCFLs (Cold Cathode Florescent Lamp) in the backlight? 
If so, perhaps your inverter that generates the high voltage strike voltage is failing.

Try this, when it goes dark, reduce the ambient light as much as possible.  Using a flashlight (torch), illuminate the screen by holding the light off to the side of the screen and point it so that it illuminates the display at a low angle.  Then, looking at the display from various angles, see if you can see a picture on the display.  If so, it might be an indication that the computer is working fine, but that the monitor is the problem.  If it is, it is likely a breakdown in the secondary winding of transformer on your inverter. 

This can be fixed. http://www.lcdparts.net/u3d.aspx
But be careful -- If you touch the inverter or its output leads while it is running, you may be doing the high voltage dance.

Last edited by ewaller (2016-06-13 14:46:34)


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#3 2016-06-13 23:14:23

asoundmove
Member
Registered: 2016-03-16
Posts: 5

Re: [Solved] - External monitor randomly blanks frequently, stays blank

Wow, you are right - I really did not think it was a hardware problem.
The low angle flashlight approach did not work for me, I could only see the screen's surface.
Instead I shone a smartphone's LED flashlight right into the screen very close-up, that revealed the image in the screen.
So off to do some DIY (unpowered off course) to check what I need.
Thank you.

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#4 2016-06-13 23:31:06

R00KIE
Forum Fellow
From: Between a computer and a chair
Registered: 2008-09-14
Posts: 4,734

Re: [Solved] - External monitor randomly blanks frequently, stays blank

Please mark this as [Solved] not as [Closed]. Solved means you found a solution to your problem, closed usually means the thread derailed without reaching a solution/conclusion.

See: https://wiki.archlinux.org/index.php/Co … ow_to_post


R00KIE
Tm90aGluZyB0byBzZWUgaGVyZSwgbW92ZSBhbG9uZy4K

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#5 2016-06-14 02:38:11

ngoonee
Forum Fellow
From: Between Thailand and Singapore
Registered: 2009-03-17
Posts: 7,354

Re: [Solved] - External monitor randomly blanks frequently, stays blank

ewaller wrote:

That is an LCD display.  You also say that it is years old; perhaps old enough to use CCFLs (Cold Cathode Florescent Lamp) in the backlight?  ....

ewaller, you never cease to amaze me.


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