Jeff@couldbeinvalid.com wrote:
> I have a Toshiba Satellite laptop M105-S3084 running Windows XP which today
> started giving me scary video problems that I do not know how to figure out.
>
> When I boot up the laptop, the screen shows the initial BIOS bootup screen
> (with "click F2 to setup .... etc." at the bottom). This stays on for 1
> second and the screen goes dark. The disc drive light goes on but nothing
> appears on the screen. I have a BIOS password, so when I guess that request
> has appeared and enter it and press enter and notice that the bootup into XP
> continues (because the drive light goes back on) but this is done blindly
> because nothing appears on the screen after the first second I mentioned.
>
> I tried rebooting numerous times with the same result. Clicking on F2, F12,
> F8 have no effect. Same behavior. Then suddenly it booted up normally with
> everything visible on the screen. I assumed the laptop system was just
> confused and now all is well. But when I rebooted it later, same problem
> occurred. Again repeated attempts at rebooting all had the same result of
> the BIOS screen appearing for 1 second followed by a blank screen. This
> time I thought this was it and nothing would work. After about 30-40
> attempts at rebooting suddenly it booted normally and this is when I am
> writing this.
>
> I have full backups at home but I am now on a trip writing from a hotel and
> will not be home till after New Year. So data loss is not a problem but I
> do not know what would be causing this weird video problem. Can you help?
>
> After this successful bootup I ran the Toshiba "PC Diagnostic Tool" and
> everything passed. I checked XP's Device Manager screen and there are no
> yellow warnings anywhere. Don't know where else to look. The video is
> integrated to the motherboard on this laptop. Could a failing cmos battery
> do this?
>
> Jeff
>
There are a few reasons for a screen to "disappear".
1) Backlight problem. Many LCD screens use CCFL lamps. This is a fluorescent
tube running at 700-1000 VAC. An "inverter" circuit, on a rectangular
assembly behind the panel, provides the voltage. The inverter provides
a higher voltage ("ignite") to start up the CCFL tube. That gives light
for the first second or two. The voltage supplied slowly drops ("burn") as
the tube heats up a bit. When there is a disagreement between the inverter
and the CCFL tube, it is most likely to show up at the "burn" point.
That means you get light for two seconds, and then the light goes out.
The inverter can't sustain the "burn" output, and chooses to turn off
in defense. Sometimes the problem is a bad connection, but it could
just as easily be a bad inverter. They're pretty cheaply built (but not
cheap to replace).
2) Screen resolution choice. An LCD screen, while being multisync, may have
limits to which it'll respond. If I set the resolution to 2560x1600, for
example, the chip receiving the high res signal may say "out of range".
That can be a reason for blanking the screen. It could be, that when
the Windows desktop appears, the resolution setting in the hardware,
is returned to a sane setting.
3) Display channel. The GPU is split into a couple display channels.
It could be, that your laptop is confused, and somehow thinks that
another video output (such as the VGA connector on the back), is the
current "primary" screen. Maybe that happens during the BIOS POST
sequence. Later, when Windows is running, it makes the proper decision
that the LCD screen is the "primary". You may have confused the laptop
recently, by plugging a monitor into the VGA port. Or something along
those lines. Think back to what you've plugged in recently, and see
if a second monitor was used recently.
4) Laptops have FN function keys, that can be used for reconfiguring
video. Typical "fun" things to do with the function keys, are
to rotate the screen 90 degrees. Perhaps your model has some
FN function that is buggering up normal displaying.
HTH,
Paul