[clug] Ubuntu 8.1 on Toshiba Tecra black screen problem]

doris ann doris at pcug.org.au
Mon May 18 08:29:34 GMT 2009

Thank you to Lana, Bob, Hal, Matt, Andrew.

In answer,
Andrew, I checked resolutions for monitor - seems ok.
Matt, I checked wires to lcd - nothing pinched or broken - all ok.
Bob, LCD is black all of the time - nothing at power up, nothing in 
response to <Ctrl><Alt><F1>/<F7>. I'm using an external monitor.
There's not even a few seconds of washed out red as before.
Lana, I have had the laptop since Feb2007, so it is out of warranty, and 
yes, the problem seems likely to be the lcd.
Hal, I'm interested in the unjamming you accomplished with IBM magic 
firmware keys, though I don't know if Toshiba has anything like that...

Further -
I tried to remove the back cover on my laptop to see if there were any 
lose connections on the mainboard, and I had hoped to reseat video cards 
- but a laptop is certainly a different construction to a desktop. It 
looks somewhat like two boards sandwiched together with various very 
short cables and connections between them. I stopped and reassembled 
everything without being able to get to check the video cards and any 
other possible lose connections.

I have just finished a clean install of Ubuntu 9.04 on my laptop to rule 
out any software induced problems that might have contributed to the 
black screen.

Anyway, after all that, I still have a black screen on my laptop. So, I 
reluctantly accept Lana's advice that it probably IS an LCD failure.

At least I know the signal is getting through to the LCD because it 
still shows a dim image when a bright light is shone directly into the 
lcd. And I know the problem is NOT the inverter, because I replaced that 
already with no improvement.

So, reluctantly I have to face a hardware repair - a replacement lcd. It 
is hard to accept because the laptop has not had rough treatment.

Thanks again,

I *think* a couple of years ago I saw backlights stop working on desktop 
LCD screens at work when particular high resolution video modes were 
selected. Maybe when you were changing settings you also upped the 
resolution, or refresh rate?


Hi Doris,
I have seen this problem occur on a client's Dell laptop before (cannot 
remember the exact model).

Same problem description, for a few days prior to the fault occurring, 
they noticed the screen "flashing", then finally one morning they 
couldn't see anything on the screen.
An external monitor worked fine, but the display was blank - upon closer 
inspection, you could *just* make out the display image.

I was able to open the screen surround, and observed that somehow the 
two wires that power the LCD backlight had become caught in the opening 
mechanism and had been cut, causing the fault.
A repair was ruled out due to the price of laptops being quite low 
comparatively, and as it functioned perfectly with an external monitor, 
it became a desktop-based laptop.

Hope that helps some.

This happened to me on FC10 with an IBM T42 equipped with an ATI Radeon 
7500 mobility video card just recently.
I thought maybe the backlight was fritzed but it seems fine again now. 
It did this accross reboots and the bios screen was also unlight. I 
unjammed it with IBM magic firmware keys to turn the backlight off then 
on. I don't know if you can do the same with your laptop.
I don't know what caused it, I don't think I was doing anything too 
funky with it before the reboot.
You would expect the intel graphics drivers you have to be pretty well 
supported given Kieth Packard is amongst the authors....
I'm not sure if that's any help or not.
Best of luck.

Hi Doris,
It is not clear, from your detailed description, that the backlight is
working at all. Does it come on at all during the BIOS Power-On Self
Tests (POST)? What if you press <F2> (or whatever) to get into the BIOS
Setup menu - is the backlight on then?

You mentioned that you used "terminal-mode" - was that using a virtual
console (ie. <Ctrl><Alt><F1> etc.)? If so, was the backlight on during
the virtual console session?

 From your description, it sounds to me like the backlight is kaput, but
that may not be the case.
Bob Edwards.

Thanks for such a detailed email, you've done a great job, and it 
definitely helps us work out where the problem might be.

I'm no expert, but from what you're saying, my call would be a dead LCD
screen. I don't believe that the changes you have made could have caused
this issue, and given that the external display works, it seems as 
though the video card and drivers are all OK. It looks as though you've 
done most reasonable checks and eliminated the obvious (and some not so 
obvious!) issues. How old is the machine? Can you contact Toshiba for a 
warranty, or if it's too old, a replacement LCD panel? (I'm not sure how 
easy the LCDs are to replace on the Toshibas, I've never attempted it, 
but they should be able to advise you).

Does anyone else have other suggestions?


-------- Original Message --------
Subject: [clug] Ubuntu 8.1 on Toshiba Tecra black screen problem
Date: Fri, 15 May 2009 13:16:30 +1000

Hi. I'm new to this list.
Can anyone offer some suggestions on this problem with my laptop, please?

Problem summary:
no backlight on laptop, black screen, no response to live cd, no change
to new inverter, it is running an external monitor ok

I'm new to Ubuntu, installed 8.1, and it was running for a couple of
months before this black screen problem occurred.

laptop Toshiba Tecra A8-S8414,
display 15.4" TruBrite TFT LCD 128x800 wxga,
Intel Graphic Media Accelerator 950, 8MB graphics memory.

Externally shining a bright light into the black laptop screen, reveals
that the text is there, but no backlight.
Just before it failed, the screen was flashing intermittantly.
Also on power-up, the screen WAS illuminating for about three seconds.

Is it something I did? A few days before the problem, I made some
changes via System/Preferences/Power Management.
Under tab "On AC Power": I moved the slider switches to different times,
and checked the box "Dim Display when idle."
Under tab "On Battery Power: Also moved the slider switches,
and checked both boxes to:"Reduce backlight brightness" and
"Dim Display when idle".

For a couple of days, it seemed to be working with those changes, but
then, flashing, and then black.

As a result of the black laptop screen, I connected an external monitor
to the system, and the external monitor works ok.

I have also removed the checks on System/Preferences/PowerManagement
boxes: "Dim Display when idle" and "Reduce backlight brightness" boxes.

Boxes unchecked, however, the problem persists on the laptop monitor.

The function key to increase brightness [Fn]+[F7] does not change the
black screen.

I saw a post (http://linuxhappy.wordpress.com/2007/12/17/bright...) that
said to try Ctrl+Alt+F1 and then Ctrl+Alt+f7.
That sequence of keys gave me three seconds viewable on my laptop
screen, although the color was red and washed out. Then it went black
Now, the black screen stays black - no response to that technique.

In terminal mode,
sudo gconf-editor /apps/gnome-power-manager/backlight
and unchecked idle_dim_battery.
That didn't make any difference to the dark screen problem.

Yet another post (http://ubuntuforums.org/archive/index.php/t-75678.html),
said to try adding a second line to /etc/acpi/resume.sh,
adding /usr/bin/toshset -bl on
Again on powerup, that made no difference either.
So, not knowing what I'm doing, I removed the line I added.

And from info on another post
(http://ubuntuforums.org/archive/index.php/t-976384.html), I ran lspci
to obtain video info:
00:02.0 VGA compatible controller: Intel Corporation Mobile 945GM/GMS,
943/940GML Express Integrated Graphics Controller (rev 03)
00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME,
943/940GML Express Integrated Graphics Controller (rev 03)

 From this http://ubuntuforums.org/showthread.php?t=1115429
I followed the directions,
esc on bootup into -11 generic (recovery)
Then selected xfix Try to fix X server
then, resume Resume normal boot
However, I still have a black laptop screen.

I tried a live cd of PuppyLinux and had the same black screen result, so
I bought an inverter and hoped it would fix the problem.

It didn't. I returned the original inverter back into the laptop.

As before, if I put a bright light against the laptop screen, I can see
the contents of the screen dimly (same contents as on my auxilliary

An external monitor connected to the laptop works ok.
Does that mean the video card is ok.

Could the problem still be the video card?
Or the LCD?
Or is it software related - because of the changes I made?

I have noted that there is a lot of discussion regarding backlights on
laptops in the Ubuntu forums.

I don't know whether to think the problem is purely hardware or
software induced.

I'm planning to do a clean install of Ubuntu 9.04 just in case the
changes I made had a temporary effect on the hardware.

Any thoughts about what the problem might be and how to fix it?

linux mailing list
linux at lists.samba.org

More information about the linux mailing list