screen blanking on Dell laptop

  • Thread starter Thread starter Nietzsche
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Nietzsche

The screen/display is blanking out on my Dell C640 Latitude laptop. It
happens when the machine has been on for about three minutes. Programs
still run and I can still listen to MP3s when it happens. Closing the
lid and opening it will bring the display back as will Fn+3 (blank
display) and then hit any key to unblank. However, the display comes
back for exactly 10 secnds before blanking itself again.

It's not an OS problem because it happens before the OS has loaded,
like when I'm in he BIOS at boot up.

Any ideas? Or should I just use it for a door stop?
 
Nietzsche said:
The screen/display is blanking out on my Dell C640 Latitude laptop. It
happens when the machine has been on for about three minutes. Programs
still run and I can still listen to MP3s when it happens. Closing the
lid and opening it will bring the display back as will Fn+3 (blank
display) and then hit any key to unblank. However, the display comes
back for exactly 10 secnds before blanking itself again.

It's not an OS problem because it happens before the OS has loaded,
like when I'm in he BIOS at boot up.

Any ideas? Or should I just use it for a door stop?
Click to expand...

screen cable connector.......may need reseating
graphics card..........may need reseating or may be on its way out.

see alt.sys.pc-clone.dell...........just had my m60 graphics card replaced.
 
Nietzsche said:
The screen/display is blanking out on my Dell C640 Latitude laptop. It
happens when the machine has been on for about three minutes. Programs
still run and I can still listen to MP3s when it happens. Closing the
lid and opening it will bring the display back as will Fn+3 (blank
display) and then hit any key to unblank. However, the display comes
back for exactly 10 secnds before blanking itself again.

It's not an OS problem because it happens before the OS has loaded,
like when I'm in he BIOS at boot up.

Any ideas? Or should I just use it for a door stop?
Click to expand...

It could be a problem with the screen backlight. There is
typically an inverter (makes 1000 VAC) and a CCFL (cold
cathode fluorescent lamp) backlight. If the inverter
detects an overload, maybe it is shutting off. That
won't stop the LCD pixels from updating, but you just
cannot see them.

As for repair, it all depends on what price you are quoted
for maintenance. I'd try to repair mine myself, because
I love shit like that. There are sites on the web that
sell replacement inverters or CCFL lamps, but the tough
part is getting exact replacements, or at least replacement
parts that play together. The inverter expects a certain
load, the CCFL expects a particular voltage, the inverter
offers certain control signals to the laptop (so you can
set the brightness and so on). Even when repaired
"professionally", there is always the possibility that
the parts are not a good match. The modules used may go out
of supply, and the substitutes used may not always be perfect.

A CCFL lamp might be good for 25000-50000 hours, but chances
are the lamp itself is not at fault. It could even be a bit
of dust shorting out the 1000 VAC, or a bad connection where
the inverter plugs into its connector.

To see pictures of someone attempting to repair/inspect,
there is an example here. Quality workmanship, is not
leaving screwdriver marks in the plastic, when you pry the
screen apart - scary stuff :-) Not all laptops disassemble
the same way, so look around the web for web pages that
have attempted repair of your particular model.

http://www.fonerbooks.com/laptop_5.htm

Paul
 
Paul said:
It could be a problem with the screen backlight. There is
typically an inverter (makes 1000 VAC) and a CCFL (cold
cathode fluorescent lamp) backlight. If the inverter
detects an overload, maybe it is shutting off. That
won't stop the LCD pixels from updating, but you just
cannot see them.

As for repair, it all depends on what price you are quoted
for maintenance. I'd try to repair mine myself, because
I love shit like that. There are sites on the web that
sell replacement inverters or CCFL lamps, but the tough
part is getting exact replacements, or at least replacement
parts that play together. The inverter expects a certain
load, the CCFL expects a particular voltage, the inverter
offers certain control signals to the laptop (so you can
set the brightness and so on). Even when repaired
"professionally", there is always the possibility that
the parts are not a good match. The modules used may go out
of supply, and the substitutes used may not always be perfect.

A CCFL lamp might be good for 25000-50000 hours, but chances
are the lamp itself is not at fault. It could even be a bit
of dust shorting out the 1000 VAC, or a bad connection where
the inverter plugs into its connector.

To see pictures of someone attempting to repair/inspect,
there is an example here. Quality workmanship, is not
leaving screwdriver marks in the plastic, when you pry the
screen apart - scary stuff :-) Not all laptops disassemble
the same way, so look around the web for web pages that
have attempted repair of your particular model.

http://www.fonerbooks.com/laptop_5.htm

Paul
Click to expand...

Thanks for the feedback. The problem went away when I turned the
screen brightness down (just a bit). Turn the brightness up and the
screen goes back to blanking every few seconds.

Wonder if that could be the inverter overload detector you mentioned.
Anyway, I can live without full brightness so it's no longer a problem.
 
Nietzsche said:
Thanks for the feedback. The problem went away when I turned the
screen brightness down (just a bit). Turn the brightness up and the
screen goes back to blanking every few seconds.

Wonder if that could be the inverter overload detector you mentioned.
Anyway, I can live without full brightness so it's no longer a problem.
Click to expand...

It is not a problem today.

But it could be a problem tomorrow. Your problem is related to
the CCFL and inverter, and it is just a matter of time, before
turning down the brightness doesn't help.

Paul
 
Paul said:
It is not a problem today.

But it could be a problem tomorrow. Your problem is related to
the CCFL and inverter, and it is just a matter of time, before
turning down the brightness doesn't help.

Paul
Click to expand...

Thanks for the advice, Paul. But this C640 has other problems: the mem
module bay #2 is not working properly and gives RAM errors, even though
the same mem tests good in bay #1. Plus the right hinge is broken and
the case is cracked. This laptop has travelled 30,000 miles in the past
4 years, has been in 2 bicycle accidents and dopped on the floor once.
I'm surprised it still lives.

Think I'm going to get an HP Pavillion dv8110us with a Turion 64
processor and 17" display.
http://www.epinions.com/Hewlett_Pac...ok_PC_EP404UA_PC_Notebook/display_~full_specs
 
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