Hi all , some times there are many laptops can not show anything on their display panel , but when I connect external display using vga port , they work will , so could I connect that port to display panel using simple circuit and thanks so much..........

Hello! Unfortunately, you can't do that because signal type on VGA port and on LCD panel are different. It seems that to make it work you only can fix what's broken on each laptop. What could be broken? I have a few suggestions.

1) Panel - the part of it that shows the image on the screen or, maybe, the matrix itself.
2) Backlight of the panel, that makes the image visible. Could be lamps or LED.
3) Invertor - the circuit that powers the backlight.
4) Cable between the panel and motherboard.
5) Cable between the invertor and motherboard
6) Some little components and connectors on the motherboard
7) Video chip on the motherboard

For each of these laptops you can have a different problem, so you have to check every one of them.

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thank you for your infomation

If you're still searching for a way to connect VGA port to LCD matrix in a laptop, I found no easy DIY ways to make a VGA-LVDS conversion adapter. The only reasonable option seems to be buying a commercial one - these aren't so cheap and, for sure, this is not something you'd use to repair a laptop.

You can use universal display scaler like this http://m.aliexpress.com/item-desc/1625909134.html