Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old September 13th 05, 01:56 AM
QJD1
 
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Default TFT Fujitsu x151f: How to reduce brightness?

Hello.

I have recently aquired an older second hand TFT monitor, Fujitsu x151f.
Otherwise it works perfectly, but there is one major problem. The
display is far too bright even when the contrast and brightness controls
are turned down to zero. If luminosity is further reduced from the video
card to acceptable elevel, the display starts to flicker. I'm now
looking for methods to reduce the luminosity of this TFT display to a
level, where one can use it and work with it without becoming blind (or
at least without headaches and serious pain in the eyes).

Any suggestion to electronically or mechanically make the display usable
is appreciated.



Best Regards
QJD1

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Old September 13th 05, 02:45 PM
Dave D
 
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Default


"QJD1" wrote in message
...
Hello.

I have recently aquired an older second hand TFT monitor, Fujitsu x151f.
Otherwise it works perfectly, but there is one major problem. The display
is far too bright even when the contrast and brightness controls are
turned down to zero. If luminosity is further reduced from the video card
to acceptable elevel, the display starts to flicker. I'm now looking for
methods to reduce the luminosity of this TFT display to a level, where one
can use it and work with it without becoming blind (or at least without
headaches and serious pain in the eyes).

Any suggestion to electronically or mechanically make the display usable
is appreciated.


I take it the controls do actually adjust the brightness, but just not as
much as you'd like? If the brightness is clearly excessive, (get a second
opinion!) It's possible there's a fault in the backlight inverter, which
left could drastically shorten the life of the backlight tubes. There could
be excessive voltage to the backlight inverter, or perhaps a failed
component on the inverter PCB itself.

If you have electronic skills then perhaps some basic troubleshooting might
bring results. If not, either live with it or get it fixed (costly, probably
not worth it). You could perhaps try one of those anti-glare screens to
reduce the brightness.

If it is working normally but just too bright for your personal tastes,
there are ways to reduce the output of backlight inverters, but that is
beyond the scope of newsgroup correspondence. An easy 'one size fits all'
way which might work could be to lower the supply to the inverter. This may
not work well as performance could become intermittent or flickery.

Dave


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Old September 13th 05, 05:38 PM
Andy Cuffe
 
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Default

On Tue, 13 Sep 2005 02:56:20 +0300, QJD1
wrote:

Hello.

I have recently aquired an older second hand TFT monitor, Fujitsu x151f.
Otherwise it works perfectly, but there is one major problem. The
display is far too bright even when the contrast and brightness controls
are turned down to zero. If luminosity is further reduced from the video
card to acceptable elevel, the display starts to flicker. I'm now
looking for methods to reduce the luminosity of this TFT display to a
level, where one can use it and work with it without becoming blind (or
at least without headaches and serious pain in the eyes).

Any suggestion to electronically or mechanically make the display usable
is appreciated.



Best Regards
QJD1



Look in the menu for a back light brightness adjustment. Some LCDs
have two brightness controls. One adjusts the black level of the
signal driving the LCD (basically doing the same thing as adjusting it
in the video card control panel) and the other adjusts the brightness
of the fluorescent tube. You don't want to adjust it with the video
card's control panel because you lose a lot of dynamic range.
Andy Cuffe

-- Use this address until 12/31/2005

-- Use this address after 12/31/2005
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Old September 13th 05, 11:55 PM
QJD1
 
Posts: n/a
Default

Dave D wrote:
I take it the controls do actually adjust the brightness, but just

not as
much as you'd like?


Yes, you are correct. I'm sure those controls work as manufacturer
intended them to work.

If you have electronic skills then perhaps some basic troubleshooting

might
bring results. If not, either live with it or get it fixed (costly,

probably
not worth it). You could perhaps try one of those anti-glare screens to
reduce the brightness.


I have basic electronic skills, and I'm taking your advice to check if
anything is wrong with the backlight inverter or other components.

If it is working normally but just too bright for your personal tastes,
there are ways to reduce the output of backlight inverters, but that is
beyond the scope of newsgroup correspondence.


This matter is really of a personal taste, I think. My eyes just can't
adjust to the brightness the monitor emits. If you have any directions
(links etc.) to help me with the problem of reducing the backlight
inverter voltage, I would appreciate it. That anti-glare screen is my
last resort to solve this problem.

Thank you for your response.


:QJD1
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Old September 14th 05, 12:04 AM
QJD1
 
Posts: n/a
Default

Andy Cuffe wrote:
Look in the menu for a back light brightness adjustment. Some LCDs
have two brightness controls. One adjusts the black level of the
signal driving the LCD (basically doing the same thing as adjusting it
in the video card control panel) and the other adjusts the brightness
of the fluorescent tube. You don't want to adjust it with the video
card's control panel because you lose a lot of dynamic range.


Unfortunately, there is no control for black level signal in this
monitor, there is only brightness and contrast. I wonder, if there is
other ways to control that black level, like dropping the voltages
feeding the backlight or otherwise modifying the circuitry.

Thank you for your response.


:QJD1


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Old September 14th 05, 06:18 AM
James Sweet
 
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Default


"QJD1" wrote in message
...
Andy Cuffe wrote:
Look in the menu for a back light brightness adjustment. Some LCDs
have two brightness controls. One adjusts the black level of the
signal driving the LCD (basically doing the same thing as adjusting it
in the video card control panel) and the other adjusts the brightness
of the fluorescent tube. You don't want to adjust it with the video
card's control panel because you lose a lot of dynamic range.


Unfortunately, there is no control for black level signal in this
monitor, there is only brightness and contrast. I wonder, if there is
other ways to control that black level, like dropping the voltages
feeding the backlight or otherwise modifying the circuitry.

Thank you for your response.


:QJD1


You may be able to add a variable resistor in the dimming circuit for the
backlight inverter, some use a simple pot to adjust it.


  #7   Report Post  
Old September 14th 05, 01:36 PM
JW
 
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Default

On Wed, 14 Sep 2005 01:04:00 +0300 QJD1 wrote in
Message id: :

Unfortunately, there is no control for black level signal in this
monitor, there is only brightness and contrast. I wonder, if there is
other ways to control that black level, like dropping the voltages
feeding the backlight or otherwise modifying the circuitry.

Thank you for your response.


How about using a black Sharpie magic marker applied to the tubes
themselves?
  #8   Report Post  
Old September 15th 05, 07:24 AM
QJD1
 
Posts: n/a
Default

QJD1 wrote:
I have recently aquired an older second hand TFT monitor, Fujitsu x151f.
Otherwise it works perfectly, but there is one major problem. The
display is far too bright even when the contrast and brightness controls
are turned down to zero. If luminosity is further reduced from the video
card to acceptable elevel, the display starts to flicker. I'm now
looking for methods to reduce the luminosity of this TFT display to a
level, where one can use it and work with it without becoming blind (or
at least without headaches and serious pain in the eyes).


Summary:

Thank You Dave D, Andy Cuffe, James Sweet and JW very much for
responding my question with excellent suggestions. I'm sure this problem
is part of history quite soon. My options to repair my monitor are now
(in that particular order):

0. Acquiring schematics and other relevant information
1. Checking circuitry for defects or faulty components
2. Adding variable resistor (pot) in the dimming circuit
3. Applying black Sharpie magic marker (or similar) to the tubes
4. Mounting anti-glare screen in front of a monitor.


THX + Best Regards

:QJD1
  #9   Report Post  
Old September 15th 05, 12:07 PM
JW
 
Posts: n/a
Default

On Thu, 15 Sep 2005 08:24:23 +0300 QJD1 wrote in
Message id: :

QJD1 wrote:
I have recently aquired an older second hand TFT monitor, Fujitsu x151f.
Otherwise it works perfectly, but there is one major problem. The
display is far too bright even when the contrast and brightness controls
are turned down to zero. If luminosity is further reduced from the video
card to acceptable elevel, the display starts to flicker. I'm now
looking for methods to reduce the luminosity of this TFT display to a
level, where one can use it and work with it without becoming blind (or
at least without headaches and serious pain in the eyes).


Summary:

Thank You Dave D, Andy Cuffe, James Sweet and JW very much for
responding my question with excellent suggestions. I'm sure this problem
is part of history quite soon. My options to repair my monitor are now
(in that particular order):

0. Acquiring schematics and other relevant information
1. Checking circuitry for defects or faulty components
2. Adding variable resistor (pot) in the dimming circuit
3. Applying black Sharpie magic marker (or similar) to the tubes
4. Mounting anti-glare screen in front of a monitor.


THX + Best Regards


Let us know which solution works for you - that way if someone else comes
along with the same question, they might be helped.

Thanks.
  #10   Report Post  
Old September 29th 05, 05:51 PM
Asimov
 
Posts: n/a
Default

"QJD1" bravely wrote to "All" (13 Sep 05 02:56:20)
--- on the heady topic of "TFT Fujitsu x151f: How to reduce brightness?"

QJ From: QJD1
QJ Xref: core-easynews sci.electronics.repair:341989

QJ Hello.

QJ I have recently aquired an older second hand TFT monitor, Fujitsu
QJ x151f. Otherwise it works perfectly, but there is one major problem.
QJ The display is far too bright even when the contrast and brightness
QJ controls are turned down to zero. If luminosity is further reduced
QJ from the video card to acceptable elevel, the display starts to
QJ flicker. I'm now looking for methods to reduce the luminosity of this
QJ TFT display to a level, where one can use it and work with it without
QJ becoming blind (or at least without headaches and serious pain in the
QJ eyes).
QJ Any suggestion to electronically or mechanically make the display
QJ usable is appreciated.


There may be issues with tube biasing. Perhaps some off value
resistors or supply voltage. Turning down g2 might do it in a pinch.

A*s*i*m*o*v

.... You mean 15" sparks are SUPPOSED to come out of this thing?!?



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