LCD issues - I need some technical advices

The screen on the laptop was turning white every now and then. The problem is a that the display cable is a bit loose in the motherboard side. Sometimes I had to unplug the display cable from the motherboard and connect it again to make the white disappear.

I did something stupid. While the battery was still inside the laptop, and while the laptop was off, I incidentally shorted out some of the pins of the socket where the display cable connect to the motherboard. The result is that I barely can see anything in the laptop LCD. It is as if the inverter is dead. The laptop was tested with an external screen and works perfectly.

I know that the screen, display cable and inverter are good. I was able to test them in another laptop and they work perfectly.

So what is damaged in the mother board and can i fix it?

Thanks.

 

I'm really not sure what that could be but I'd guess it has to be a voltage regulator or some other components specific to the inverter power.
Are you having any other power issues? If not, thats good and probably lucky.

However - you can fix it, I think. Do you have a multimeter?

I'm not totally sure on the details, and this hasn't really been done before, but I think inverters just run on plain NB voltage - you could identify the Vin and Vout in the inverter, then wire your cable to your DC jack. Or maybe the battery connector. Some datasheets - of any laptop, or inverter - might help a lot.

The fact that there is anything between the inverter input and normal laptop power makes me think its actually 12v like many generic inverters that come with VGA/DVI input LVDS panel boards. So you could always attempt to get your own voltage regulation circuit.

 

I am betting you have fried something on the motherboard, most likely a trace carrying power, although I really doubt the machine was truly off when you shorted it out as the screen would really be off if the machine was truly off.

Or you shorted something in the power/switch riser board. Also don't wire the inverter to the DC jack as suggested above, this will guarantee a dead inverter. Most inverters are 12VDC input and most jacks are 16-20VDC.

See if you can see any burnt out traces on the motherboard. It is also possible you burnt out a trace on the flex cable from the mobo to the LCD, so check there. ...

Actually, you say you know the screen flex and inverter are good so it must be the mobo. Have a quick look but I'm betting you need a new mobo.....

 

If the screen, inverter and display cable are good, the only thing left is the motherboard, or the connection on the motherboard. Diagnosing a system of a process of elimination.

 

He said he already knew it was the motherboard. So, very helpful of you guys to point that out.

Thanks for clarifying, you know there is no need to be afraid to address me directly.
As I said I suspected they might be 12v.

I dont doubt the motherboard was truly off at all, plenty of people have fried MXM slots and things with just a battery in.

In any case a new motherboard is not necessary as backlighting is incredibly simple in concept. I would recommend selling the good LCD, getting a good one with a dead backlight, removing the white paper on the back and wiring some flat LEDs directly behind it with some tinfoil as a reflector if your laptop doesn't have it already.

 

No other issues. I'm sure a fried one or more of the components that output voltage to the inverter.

I have a multimeter. How do I go about identifying the Vin and Vout pins?

The laptop was off. I guess there was some left over current in the system or something like it.

Thanks for the info.

The display cable is good. I'm sure I burned something in the motherboard.

 

Actually, I've mismatched multiple inverters from entirely different laptops pretty reliably even when some pins are not plugged in, only losing backlight control.

This leads me to believe the plain voltage is almost always the top 2 pins when the inverter is facing you. Whichever is + and - its always the same on notebooks with somewhat normal inverters unlike dells.

You'd have to try and test the pins while running it in another notebook, which may not be a good idea. I dont know a lot about voltage testing so you'll have to ask someone else. I was going to say why bother until you build a 20 to 12v voltage regulator... but I suppose if you have a 11v battery it could work out well.