LCD Black

[Florian]

Hi,

I have a LCD display that has the following symptoms. You turn it on and
the power light comes on. The monitor detects whether it is connected to
a computer (the light flashes or is always on) but the screen is black.
You can see absolutely nothing.

I tried replacing the inverter (this is the first time I ever attempted
to repair a LCD - but's it's a touchscreen and was rather expensive) but
that didn't have ANY effect.

What else could be wrong with the display, assuming it's not the main
circuit board since the power light works correctly?

Any hints are welcome, thank you!

 

[Sam Goldwasser]

Florian <REMOVEALLUPPERCASEwizard_oz@gmx.net> writes:

Hi,

I have a LCD display that has the following symptoms. You turn it on
and the power light comes on. The monitor detects whether it is
connected to a computer (the light flashes or is always on) but the
screen is black. You can see absolutely nothing.

I tried replacing the inverter (this is the first time I ever
attempted to repair a LCD - but's it's a touchscreen and was rather
expensive) but that didn't have ANY effect.

What else could be wrong with the display, assuming it's not the main
circuit board since the power light works correctly?

Just about everything. Power supply, logic, wiring, etc. If the screen
is totally black, then the backlight still isn't working since there would
always be some leakage for dark pixels. If there is low level light all
over, then the backlight is working but the LCD drive circuitry isn't.
Sometimes you can shine a bright light at the screen and faintly see the
display if the drive is functional but the backlight isn't.

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[Florian]

I have a LCD display that has the following symptoms. You turn it on and
the power light comes on. The monitor detects whether it is connected to
a computer (the light flashes or is always on) but the screen is black.
You can see absolutely nothing.

I tried replacing the inverter (this is the first time I ever attempted
to repair a LCD - but's it's a touchscreen and was rather expensive) but
that didn't have ANY effect.

What else could be wrong with the display, assuming it's not the main
circuit board since the power light works correctly?

Any hints are welcome, thank you!


Sounds like either the backlight tube has failed, or the inverter isn't
getting either a supply or volts on the brightness control pin.

Is it possible for me to find out whether the backlight is working or not?
Should I use what Sam suggested - putting a bright light towards the screen?

Thank you.

 

[Florian]

I have a LCD display that has the following symptoms. You turn it on
and the power light comes on. The monitor detects whether it is
connected to a computer (the light flashes or is always on) but the
screen is black. You can see absolutely nothing.

I tried replacing the inverter (this is the first time I ever
attempted to repair a LCD - but's it's a touchscreen and was rather
expensive) but that didn't have ANY effect.

What else could be wrong with the display, assuming it's not the main
circuit board since the power light works correctly?

Just about everything. Power supply, logic, wiring, etc. If the screen
is totally black, then the backlight still isn't working since there would
always be some leakage for dark pixels. If there is low level light all
over, then the backlight is working but the LCD drive circuitry isn't.
Sometimes you can shine a bright light at the screen and faintly see the
display if the drive is functional but the backlight isn't.

I don't think that the power supply is bad since some basic logic is still
working (like plugging the VGA cable in). Maybe it is the backlight after
all? I will try to see if the screen works with a flashlight.

Thank you.

 

[Dave D]

"Florian" <REMOVEALLUPPERCASEwizard_oz@gmx.net> wrote in message
news:49ccf36407de6b97c45171fb72a647b2@free.teranews.com...

Hi,

I have a LCD display that has the following symptoms. You turn it on and
the power light comes on. The monitor detects whether it is connected to
a computer (the light flashes or is always on) but the screen is black.
You can see absolutely nothing.

I tried replacing the inverter (this is the first time I ever attempted
to repair a LCD - but's it's a touchscreen and was rather expensive) but
that didn't have ANY effect.

What else could be wrong with the display, assuming it's not the main
circuit board since the power light works correctly?

Any hints are welcome, thank you!

Sounds like either the backlight tube has failed, or the inverter isn't
getting either a supply or volts on the brightness control pin.

Dave