Laptop Backlight Problem

[Malcolm H]

Hi Hope someone can help with my laptop problem.

I have a Fujitsu Seimens M3438G which has a defective backlight. I've replaced the inverter board but no change.

Here is the thing, if I short the metallic screen surround to one of the mounting screws on the inverter board the backlight lights and stays on.

I think the problem may be the lid switch but I can't find it anywhere. Looked for a mechanical switch and a magnet operated reed switch but nothing in the vicinity of the hinges looks likely.

Any help gratefully received.

Malcolm

[Dimitris76]

The switch you are looking for might not be on the lid/screen itself.
Pretty often it's located on the laptop's main body - somewhere on the top part of the keyboard. It's like a small pin that protrudes above the surface and is being pressed by the lid when you close it.

Dimitris

[Malcolm H]

Thank you for that Dimitris,

I am well aware that the switch is often in the main body as it is in my Acer and Toshiba laptops but this Fujitsu doesn't appear to have one anywhere!

Malcolm

[andrew b]

Could be a mercury switch or a magnetic reed switch?

[ZAGNUT]

i would expect both the screen frame and inverter board screws to be grounded to the motherboard at all times so maybe your problem is with something like the ribbon cable or a corroded connector?



dave

[Pete P]

Inside the cable from the inv->mobo or LCD-->mobo there is a ground strap, which is supposed to be screwed into the motherboard. Might be frayed, missing.

Why dont you just run a wire from the laptop LCD frame to a ground?? :-D

[thanhTran]

My Fujitsu P5020 has a switch on the right hinch facing towards the left hinch. It's very small and is triggerd by a bump on the the moving part of the hinch. I think this switch just serves as a signalling switch (no transfer power.)

It sounds like you have some broken wire some where? I would think people put switch on positive wire and not the negative on.