Lenovo SL400 Backlight

Posted on 2010-11-15
Last Modified: 2012-05-10
Alright, so the issue is the following...

The computer came into the shop with no back light. With the lack of testing hardware that matched the laptop I attempted a few different screens and a few different inverters, with no luck.

I then proceeded to order an inverter. Once the inverter arrived I still had the same problem. No back light. But I could see the image on the screen. Externally it also works perfectly fine.

So I tried a few other screens with it. Still no joy. Some of the screen didn't display due to incompatibility. But a few others did display with no back light. I cannot take this as a bad screen just yet, hence why I am here.

Has anyone encountered same problem?

Any additional information let me know.

Question by:arsgao
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LVL 48

Expert Comment

ID: 34140657
LVL 12

Expert Comment

ID: 34141021
Just thinking but ceck the cables and wieres that go to that inverter from the motherboard.

Use a multimeter set to beep when there is a shared connection and test and see if one of those components is bad .

If they are good then possibly something on the mother board not doing is job.

Author Comment

ID: 34141095
Thats a clever answer, but the Lenovos does not have LID buttons. At least from what I have been looking at.

The feature is built somewhere else, where i dont quite know where.
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Author Comment

ID: 34141107
I also know that the wires are good. at least the inverter one. I checked the connections they all beep
LVL 12

Expert Comment

ID: 34141955
What is the voltage coming out at the inverter ?
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Expert Comment

ID: 34141978
Im sorry I ment KHz.
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Expert Comment

ID: 34141984
I am wondering with the new inverter that something is not working on the motherboard.

Was you able hook up this screen to a differnt laptop to see if it would work ?
LVL 12

Expert Comment

ID: 34142199
If you can test this screen on a differnt laptop this would verify the screen is good.
 You do not have to hook up the screen cable ,
just the power cable from the back light  
to the inverter of a different laptop to see if that laptop will light the CCFL bulb in this  screen.
LVL 12

Accepted Solution

Grant1842 earned 500 total points
ID: 34142295
You can test if the LCD cable from the the mother board is supplying voltage to the inverter board.

NOTE: Do not short any pins together with the probes.
This is a voltage test so laptop needs to be running.

Place the red probe on pin one of the leg coming out of the LCD plug and going into the inverter board, and the black probe to a ground (screw hole on inverter board).

If it is supplying power to the inverter board then it has to be the inverter board or the CCFL bulb I would think.

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