Laptop inverter mysterious problem

Eliot Rosewater

A few months ago the screen on my laptop went dead. Well, not exactly dead: if you shone a powerful lamp on it you could still see the stuff on screen. I was informed that this was simply a backlight problem, and to change the inverter.

So I bought a new inverter and installed it, but that didn't fix anything. So is there anything I can do now? Bin the laptop?

dazzday

Certainly dont bin it yet!

Screen failure can be narrowed down to the following in likely order:

- Loose connections
- Faulty or stuck Lid Switch
- Faulty inverter
- Faulty backlight
- Faulty VGA cable
- GPU card issues
- Motherboard issues

My advice is to take off the bezel again and reset all connections you see, check the cables for any signs of obvious damage and if any crimping of cabes is evident. Suprisingly this will solve 90% of problems.

Try and locate the lid-switch. In many machines this will be a mechanical switch or button located just below the screen under the power butoon bezel that is responsible for swithing off the screen once closed. In many cases it can become stuck due to dirt etc and just needs cleaning. Try pressing it a number of times and see if that works. If you cant locate the switch, it may be magnetic, in which case failure is unlikely. You can if you wish run a magnet over the top end of the bezel and locate it, however id reccomend removing your HDD before so.

Inverter and backlight failure unfortunately carrier the same symptoms.
If you have access to a multimeter ( need to be 50KHz plus range) you can connect the two probes together and hover them above the inverter location when the laptop is on ( no need to touch the board. It is at high voltage and damage may occur). If you can detect the frequency cycle output from background the inverter is functioning correctly.

Another option is purchasing a working backlight tube with connections already attached. (only a couple of dollars)



If connected directly to the inverter and working, you can narrow the problem down to backlight failure. Replacing a backlight is a horribly tedious and difficult task, involving taking apart the lcd screen and soldering on wires etc. Many technicians wont do it and will reccomend a new screen. However if you are technically competent and have some time on your hands, it is worth a go as worst case scenario is buying a new screen anyways.

Faulty VGA cable is simply a replacemnt and hope for the best change. Quite unlikely however and should be noticable if damage is evident.

In your case GPU issues seems ok. However first thing id do is plug the laptop up to an external display. If you get no signal then we have opened up a new kettle of fish of problems.

And if nothing else works, just pray it isnt a serious mobo issue!

Eliot Rosewater

Wow, that's an extensive post!

It definitely is inverter or back-light failure: I can see the screen with a bright light and an external monitor works.

I don't have access to a multimeter with such a range, unfortunately.

To be honest, it's an old laptop and I've already spent enough money on inverters. I think I'll just leave it.

dazzday

Did you try the lid switch? suprisingly common problem.

Eliot Rosewater

It's definitely not the switch!

But, I'm not going to bin it - I had a eureka moment last night in which I realized I could use it as a second PC to teach myself networking. So I wiped it, installed Ubuntu 10.04 and am typing from it now! Cheers for the help again.