LCD negative image

[opsdire]

My daughter has a Toshiba P105 laptop with a 17 inch LCD monitor. The image is very dark and is a negative image. I have replaced the inverter and both backlights appear to be working. It is not a close switch issue, I have checked it. When connected to an external monitor the image is correct. I am out of ideas and need some help in finding another direction.

[zeroth]

I have the same issue with an HP laptop and could not resolve it. Finally just put a flat screen and wireless keyboard/mouse on it and use it as a desktop. I think the displays either just give up or it could be a connection came loose opening and closing it so much. You can google instructions for replacing the display and see if you can see something loose but if you aren't savvy in this activity, don't try it.

[AIon01]

My daughter has a Toshiba P105 laptop with a 17 inch LCD monitor. The image is very dark and is a negative image. I have replaced the inverter and both backlights appear to be working. It is not a close switch issue, I have checked it. When connected to an external monitor the image is correct. I am out of ideas and need some help in finding another direction.

Hi Opsdire!

Did you find a solution for your daughter's laptop? My laptop has got the same problem ... and I'm looking for a suggestion to solve it.

AIon

[bluecat12]

My daughter has a Toshiba P105 laptop with a 17 inch LCD monitor. The image is very dark and is a negative image. I have replaced the inverter and both backlights appear to be working. It is not a close switch issue, I have checked it. When connected to an external monitor the image is correct. I am out of ideas and need some help in finding another direction.

Press the Control-Option-Command-8 key combination. This is actually a feature of Universal Access that you can toggle.

[tew]

I had the same problem with a Toshiba A105 laptop and was able to fix it.
Up front, I have to say that:

1) You shouldn't try this unless you have some expertise in fixing electronics and are comfortable disassembling laptops. Especially since it involves working
with the LCD inverter board which provides high voltage to the fluorescent
backlight tube.

2) Though the symptoms may seem similar, your problem may not be what I found.
So keep that in mind.

Just before LCD went into negative image mode, I had noticed a few times
when the screen would seem to darken intermittently, I thought maybe the
power cord was loose and the system was falling into a power save mode but
now I think this was the warning sign.

When the failure occurred it was immediate and never recovered. At the time,
I thought the backlight had crapped out. But after disassembling the lid
and re-powering I could see the backlight shining from the back of the LCD
assembly. I then checked for loose wires and cabling connections with no
luck. Finally, since the inverter was covered by a thin plastic cover, I
started pressing lightly on parts of the inverter board for bad solder joints
and cracked traces. Bingo! I was able get the screen back by pressing on
an SMT potentiometer with the reference designator VR1. I threw an ohmmeter
across the outside leads and found it was 10K but the measurement from one
side to the wiper was only about 500 ohms. I tried to de-solder
the pot but it cracked and broke during the effort - very fragile. Since
I didn't have a matching part, I replaced it temporarily with a 10K 10-
turn through-hole part just to find a good setting. I went with about
1200 ohms by turning and eyeballing the contrast of the screen, though it
was pretty subtle. I removed the pot and substituted two 0604 chip resistors
to match the pot setting. Powered back up and it works like a champ. Though,
as I said before, your mileage may vary.