[clug] Ubuntu 8.1 on Toshiba Tecra black screen problem]
bob at cs.anu.edu.au
Tue May 19 01:58:16 GMT 2009
doris ann wrote:
> 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?
Given your previous description of the LCD/backlight giving some
intermittent light for a while which has now stopped, I definitely
would point the finger at the backlight. You mention that you have
replaced the DC-DC inverter for the backlight and that didn't make
any difference, and you have checked the wires, so I would point my
finger (without actually having seen the thing myself) at the cold-
cathode flourescent tube - the actual backlight itself. As other
posters have mentioned, these can be replaced and can also be replaced
by LEDs or other light-emitting devices, but it will take a bit of
fiddling. Alternatively, use it as a low-power desktop, or as a router
(the built-in battery makes a decent UPS).
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