Laptop boots to blank screen

someone_else wrote:


I tried Memtest boot disk, Knoppix live cd and Windows XP install disk.
Nothing appeared on screen, they all spun in the drive for a second but
nothing seemed to happen after that. I tried pressing a key or two (return
for example) to see if any seeks were initiated but no joy, no noises from
the CD drive.

Any ideas on why the laptop no longer makes it to the windows logo screen,
when a couple of days ago it made it into windows, once, and then froze?

Here's a theory: Maybe there was a loose wire/connection to the GPU/LCD,
maybe it came loose (er) and caused a short, causing the laptop to refuse to
continue the POST.

Think I'll take it apart again, this time I'll look at the connections to
the LCD, they are not easy to follow unless it's completely disassembled.

On a desktop, I'd use a "beep test" as a test case.

Removing the RAM on a desktop, causes the processor to beep the
PC speaker. It proves two things. The computer realizes it doesn't
have any RAM. But the beep sound is made under program control,
and when you hear the "beep", you know the processor went down
through the Northbrdge and Southbridge, and read code from the
BIOS EEPROM. So it executed some BIOS code, in order to know
how to beep.

Sometimes, bad RAM will cause the BIOS program to get stuck, and
it cannot beep even though the RAM is bad. If removing the RAM,
gives a beep, then you'd suspect bad RAM was holding it
hostage.

You need to concentrate on some lower level tests, and
give up on Windows for now.

Simplify the setup. Disconnect the hard drive and optical
drive cabling. Experiment with removing the memory.

A laptop may have an LCD display, but it also has a VGA
or DVI connector on the back. You can try plugging a monitor
in there, if you suspect the LCD is no longer working.

The most likely cause of a "black" LCD screen, is a
backlight failure. There is a CCFL tube behind the
screen, that provides the light. The tube is driven
by a small board called an inverter. It converts 12VDC
to 1000 VAC at low current. That is what causes the CCFL
gas filled tube to light up. The CCFL draws about 3 watts
of power, so is not a strong light source. The "LCD"
part of the display is more reliable than the light
source.

But just as easily, a failure to execute BIOS code, will also
cause a black screen (GPU not programmed etc). So you cannot
for certain, associate a black screen, with a bad backlight.
It could be black for other reasons.

I see no reason to play with the LCD at the moment. If you
know your laptop beeps at startup, work with that to start
with. And if you really think the display is busted, use
an external LCD monitor and a VGA cable.

There is probably some key you press, to get into the BIOS.
On the machines here, the two different keys they use, are
the Delete key and F2. Different brands of computers choose
to use a different key, so check the user manual to know
for sure. "Fn F5" might change the display, to use the
external VGA, but that would only work if some software
is there to intercept the key press. As far as I know,
switching to the VGA connector is not a direct hardware
type feature.

Getting into the BIOS is an even lower level check than
trying to run Windows. Seeing the name of the hard drive
and of the optical drive, in the BIOS, would be proof
of a little bit of communications working with them.

The inside of the laptop contains power conversion circuits.
They convert battery voltage, into lower voltages that run
the logic. Your symptoms are also consistent with a failure
in those circuits. Even bad capacitors could do it (give
variable startup results, run for a short period of time and
so on). It isn't necessarily a logic failure - it could be
related to how things are powered internally.

Good luck,
Paul

"Paul" wrote in message
...
someone_else wrote:


I tried Memtest boot disk, Knoppix live cd and Windows XP install disk.
Nothing appeared on screen, they all spun in the drive for a second but
nothing seemed to happen after that. I tried pressing a key or two
(return for example) to see if any seeks were initiated but no joy, no
noises from the CD drive.

Any ideas on why the laptop no longer makes it to the windows logo
screen, when a couple of days ago it made it into windows, once, and then
froze?

Here's a theory: Maybe there was a loose wire/connection to the GPU/LCD,
maybe it came loose (er) and caused a short, causing the laptop to refuse
to continue the POST.

Think I'll take it apart again, this time I'll look at the connections to
the LCD, they are not easy to follow unless it's completely disassembled.

On a desktop, I'd use a "beep test" as a test case.

Removing the RAM on a desktop, causes the processor to beep the
PC speaker. It proves two things. The computer realizes it doesn't
have any RAM. But the beep sound is made under program control,
and when you hear the "beep", you know the processor went down
through the Northbrdge and Southbridge, and read code from the
BIOS EEPROM. So it executed some BIOS code, in order to know
how to beep.

Sometimes, bad RAM will cause the BIOS program to get stuck, and
it cannot beep even though the RAM is bad. If removing the RAM,
gives a beep, then you'd suspect bad RAM was holding it
hostage.

You need to concentrate on some lower level tests, and
give up on Windows for now.

Simplify the setup. Disconnect the hard drive and optical
drive cabling. Experiment with removing the memory.


I removed the memory, and the hard disk, no beeps. The laptop did not
change
its behaviour.

A laptop may have an LCD display, but it also has a VGA
or DVI connector on the back. You can try plugging a monitor
in there, if you suspect the LCD is no longer working.

I connected a monitor to the VGA socket, "fn" "F5" keys should toggle
from
the LCD to the VGA,
but it received no signal.


The most likely cause of a "black" LCD screen, is a
backlight failure. There is a CCFL tube behind the
screen, that provides the light. The tube is driven
by a small board called an inverter. It converts 12VDC
to 1000 VAC at low current. That is what causes the CCFL
gas filled tube to light up. The CCFL draws about 3 watts
of power, so is not a strong light source. The "LCD"
part of the display is more reliable than the light
source.

But just as easily, a failure to execute BIOS code, will also
cause a black screen (GPU not programmed etc). So you cannot
for certain, associate a black screen, with a bad backlight.
It could be black for other reasons.

I see no reason to play with the LCD at the moment. If you
know your laptop beeps at startup, work with that to start
with. And if you really think the display is busted, use
an external LCD monitor and a VGA cable.

I'm not suspecting the LCD display itself but .. have my eye on the
Graphics
controller or connection from, also now... as you mentioned it ....
some
dodgy capacitor or other circuit. ....The reason I think the LCD
display
is still good is because it displayed the window logo 2 days ago, and
the
system froze, rather than the display failing. Since then the boot
process
has not got as far as the LCD IMHO

...... ......

cheers!

On 6 Apr, 08:21, Paul wrote:
someone_else wrote:

I tried Memtest boot disk, Knoppix live cd and Windows XP install disk.
Nothing appeared on screen, they all spun in the drive for a second but
nothing seemed to happen after that. I tried pressing a key or two (return
for example) to see if any seeks were initiated but no joy, no noises from
the CD drive.

Any ideas on why the laptop no longer makes it to the windows logo screen,
when a couple of days ago it made it into windows, once, and then froze?

Here's a theory: Maybe there was a loose wire/connection to the GPU/LCD,
maybe it came loose (er) and caused a short, causing the laptop to refuse to
continue the POST.

Think I'll take it apart again, this time I'll look at the connections to
the LCD, they are not easy to follow unless it's completely disassembled.

On a desktop, I'd use a "beep test" as a test case.

Removing the RAM on a desktop, causes the processor to beep the
PC speaker. It proves two things. The computer realizes it doesn't
have any RAM. But the beep sound is made under program control,
and when you hear the "beep", you know the processor went down
through the Northbrdge and Southbridge, and read code from the
BIOS EEPROM. So it executed some BIOS code, in order to know
how to beep.

Sometimes, bad RAM will cause the BIOS program to get stuck, and
it cannot beep even though the RAM is bad. If removing the RAM,
gives a beep, then you'd suspect bad RAM was holding it
hostage.

You need to concentrate on some lower level tests, and
give up on Windows for now.

Simplify the setup. Disconnect the hard drive and optical
drive cabling. Experiment with removing the memory.


I removed the memory, and the hard disk, no beeps. The laptop did not
change
its behaviour.


A laptop may have an LCD display, but it also has a VGA
or DVI connector on the back. You can try plugging a monitor
in there, if you suspect the LCD is no longer working.


I connected a monitor to the VGA socket, "fn" "F5" keys should toggle
from
the LCD to the VGA,
but it received no signal.



The most likely cause of a "black" LCD screen, is a
backlight failure. There is a CCFL tube behind the
screen, that provides the light. The tube is driven
by a small board called an inverter. It converts 12VDC
to 1000 VAC at low current. That is what causes the CCFL
gas filled tube to light up. The CCFL draws about 3 watts
of power, so is not a strong light source. The "LCD"
part of the display is more reliable than the light
source.

But just as easily, a failure to execute BIOS code, will also
cause a black screen (GPU not programmed etc). So you cannot
for certain, associate a black screen, with a bad backlight.
It could be black for other reasons.

I see no reason to play with the LCD at the moment. If you
know your laptop beeps at startup, work with that to start
with. And if you really think the display is busted, use
an external LCD monitor and a VGA cable.


I'm not suspecting the LCD display itself but .. have my eye on the
Graphics
controller or connection from, also now... as you mentioned it ....
some
dodgy capacitor or other circuit. ....The reason I think the LCD
display
is still good is because it displayed the window logo 2 days ago, and
the
system froze, rather than the display failing. Since then the boot
process
has not got as far as the LCD IMHO


cheers!

- Show quoted text -

Well I dis-assembled the laptop but could not see anything wrong on
the motherboard (no burnt components, loose wires, degraded soldering,
bulging capacitors).

When I re-assembled it and pressed the power button, (just to make
sure the behaviour was the same since re-assembly) IT booted to the
blanks screen as usual. Then I powered down using the press and hold
method. On powering up again it halted on this screen:
http://i30.photobucket.com/albums/c3...corruption.jpg

It's the 'Windows did not boot up correctly" menu where you can choose
"boot windows normally" etc. In any case the system froze on that
screen and I tried to boot up again, but it was then back to business
as usual, (boots to blank screen/ reboots over and over)

So unless anyone has any other ideas I am going to call this laptop a
right off. ( some component has failed on the motherboard - sorry I
can't fix it - here is the name of a laptop repair shop they will
likely say it needs a new motherboard - it'll cost more than the
laptop is worth)

cheers!

On 6 Apr, 14:52, wrote:
Well I dis-assembled the laptop but could not see anything wrong on
the motherboard (no burnt components, loose wires, degraded soldering,
bulging capacitors).

When I re-assembled it and pressed the power button, (just to make
sure the behaviour was the same since re-assembly) IT booted to the
blanks screen as usual. Then I powered down using the press and hold
method. On powering up again it halted on this screen:http://i30.photobucket.com/albums/c3...synoteRscreenc...

It's the 'Windows did not boot up correctly" menu where you can choose
"boot windows normally" etc. In any case the system froze on that
screen and I tried to boot up again, but it was then back to business
as usual, (boots to blank screen/ reboots over and over)

So unless anyone has any other ideas I am going to call this laptop a
right off. ( some component has failed on the motherboard - sorry I
can't fix it - here is the name of a laptop repair shop they will
likely say it needs a new motherboard - it'll cost more than the
laptop is worth)

cheers!

I meant to say, the text on the image is corrupt, almost unreadable.
What would cause that?

wrote:
On 6 Apr, 14:52, wrote:
Well I dis-assembled the laptop but could not see anything wrong on
the motherboard (no burnt components, loose wires, degraded soldering,
bulging capacitors).

When I re-assembled it and pressed the power button, (just to make
sure the behaviour was the same since re-assembly) IT booted to the
blanks screen as usual. Then I powered down using the press and hold
method. On powering up again it halted on this screen:http://i30.photobucket.com/albums/c3...synoteRscreenc...

It's the 'Windows did not boot up correctly" menu where you can choose
"boot windows normally" etc. In any case the system froze on that
screen and I tried to boot up again, but it was then back to business
as usual, (boots to blank screen/ reboots over and over)

So unless anyone has any other ideas I am going to call this laptop a
right off. ( some component has failed on the motherboard - sorry I
can't fix it - here is the name of a laptop repair shop they will
likely say it needs a new motherboard - it'll cost more than the
laptop is worth)

cheers!

I meant to say, the text on the image is corrupt, almost unreadable.
What would cause that?

Your link got cut off, due to the way Google Groups behaves. By pulling
the original article from the Google server, I got the whole URL.

http://i30.photobucket.com/albums/c3...corruption.jpg

As far as I know, the LCD screen is pixel addressable. That means
for a letter to be displayed as a different letter, that function
is not in the LCD itself. Something else does the translation from
a byte containing the ASCII character, into a bitmap. It could be
done by the OS. It might even be possible to program that
function into a GPU. Both the GPU and the OS, have some RAM to
work with.

The corruption doesn't seem to have a pattern, but perhaps you can
see one. The ASCII codes are here, with the hexadecimal table showing
the 8 bit code and its letter equivalent.

http://www.manpagez.com/man/7/ascii/

It almost looks like the translation going on, might not be
one to one. So two input characters like "e" and "f", might
be giving the same output character. The hex value 0x20,
which is a space, might be rendered as "!" for example.
So the display itself is not corrupt, but the translation
process attempting to display characters on the screen, is.
And I don't know enough about Windows, to say whether the
current screen is a "terminal emulation mode" supported by
the GPU, or is done entirely by the OS itself.

Paul

On 6 Apr, 17:44, Paul wrote:
wrote:
On 6 Apr, 14:52, wrote:
Well I dis-assembled the laptop but could not see anything wrong on
the motherboard (no burnt components, loose wires, degraded soldering,
bulging capacitors).

When I re-assembled it and pressed the power button, (just to make
sure the behaviour was the same since re-assembly) IT booted to the
blanks screen as usual. Then I powered down using the press and hold
method. On powering up again it halted on this screen:http://i30.photobucket.com/albums/c3...synoteRscreenc...

It's the 'Windows did not boot up correctly" menu where you can choose
"boot windows normally" etc. In any case the system froze on that
screen and I tried to boot up again, but it was then back to business
as usual, (boots to blank screen/ reboots over and over)

So unless anyone has any other ideas I am going to call this laptop a
right off. ( some component has failed on the motherboard - sorry I
can't fix it - here is the name of a laptop repair shop they will
likely say it needs a new motherboard - it'll cost more than the
laptop is worth)

cheers!

I meant to say, the text on the image is corrupt, almost unreadable.
What would cause that?

Your link got cut off, due to the way Google Groups behaves. By pulling
the original article from the Google server, I got the whole URL.

http://i30.photobucket.com/albums/c3...synoteRscreenc...

As far as I know, the LCD screen is pixel addressable. That means
for a letter to be displayed as a different letter, that function
is not in the LCD itself. Something else does the translation from
a byte containing the ASCII character, into a bitmap. It could be
done by the OS. It might even be possible to program that
function into a GPU. Both the GPU and the OS, have some RAM to
work with.

The corruption doesn't seem to have a pattern, but perhaps you can
see one. The ASCII codes are here, with the hexadecimal table showing
the 8 bit code and its letter equivalent.

http://www.manpagez.com/man/7/ascii/

It almost looks like the translation going on, might not be
one to one. So two input characters like "e" and "f", might
be giving the same output character. The hex value 0x20,
which is a space, might be rendered as "!" for example.
So the display itself is not corrupt, but the translation
process attempting to display characters on the screen, is.
And I don't know enough about Windows, to say whether the
current screen is a "terminal emulation mode" supported by
the GPU, or is done entirely by the OS itself.

* * Paul- Hide quoted text -

- Show quoted text -

Interesting stuff thanks. I have called it quits on this laptop, the
owner has decided to purchase a replacement. It's a shame, but
sometimes it works out like that.

Thanks to all who tried to help me out.

I suspect that the CPU is dead. Sounds like power is getting to the
motherboard.

Chieh


On Apr 4, 5:48*pm, "someone_else"
wrote:
Hi all,
I received a laptop to fix today .. It behaves like it is overheating but
I'm not sure.

When the power button is pressed the laptop fan whirs for about 2 seconds
and then nothing happens the screen is left blank, no further activity.

If I pull the power cable out, push it back in, then press the power button
the same thing happens,

However if I power down by holding the power button for 7 seconds (leaving
the power cable attached); the fan whirrs for 2 seconds as before, but then
the laptop appears to cut the power (as if it is overheating) ... then 2
seconds later the fan whirrs on as if the laptop is rebooting. Nothing
appears on the screen ..

I did manage to boot as far as the windows logo by leaving the laptop in *a
cold room for an hour and then trying.

So you see why it points to overheating .. but on the other hand when I feel
the heatsink with my finger it does not feel too hot at all! (I had another
laptop overheat, and it felt hot alright)

any ideas?

wrote:

I suspect that the CPU is dead. Sounds like power is getting to the
motherboard.

Please do not top-post. Your answer belongs after (or intermixed
with) the quoted material to which you reply, after snipping all
irrelevant material. Notice how the quotations have disappeared
because of your top-posting. See the following links:

http://www.catb.org/~esr/faqs/smart-questions.html
http://www.caliburn.nl/topposting.html
http://www.netmeister.org/news/learn2quote.html
http://cfaj.freeshell.org/google/ (taming google)
http://members.fortunecity.com/nnqweb/ (newusers)

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: http://cbfalconer.home.att.net
Try the download section.