Laptop Screen Dims !?!

[Jodo]

Could do with some help as I've never seen anything like this before!

The laptop is a friends eMachines W340UA.

Recently, the screen has started dimming right down during bootup. If you look closely you can just see the pointer and still work but it is nearly totally black. If you then almost close the screen, open it up again, it will come back on for a few seconds, then go off again!

This only works a couple of times, then you usually need to shut the lid to go to standby and then re-open.

I've checked everything I can think of. Power settings are all set to "Always On" and I've disabled dimming in the BIOS, but it happens in the BIOS also so I guess that rules out any Windows settings.

Only other thing I can think of is that the inverter is on the way out. The screen seems quite dim anyway for the few seconds it displays properly.

Anyone have any experience of how an inverter fails? Does it just go or do you get the symptoms above?

Thanks.

[Funkstar]

Could be the inverter, or the actual backlight itself. I've seen one go on a Toshiba laptop at work.

We just replaced the whole laptop, much easier and although it wouldn't have been due for a replacement otherwise, it was a couple of years old.

[da_ging]

sounds very much like the inverter, a pretty easy fix and you will probably be able to get on off of ebay for £10-£15 just make sure you get the right one

[GoNz0]

agree with the above posts, its not often the lamp.

[Jodo]

Thanks guys. Pretty much the conclusion I had muddled my way to (not having much experience of laptops ).

He doesn't have the cash to buy a replacement so I think I'll try the repair with a used inverter.

[GoNz0]

see if you can google the destruction book to get the screen cover off, otherwise look for all the screws (and covers) then use a credit card to pop the lid open

[Jodo]

Just thought I'd update you guys on this and ask for more advice....

The replacement inverter arrived today. It was a fairly easy job to replace....but...switched on and the problems are still there.

Anybody have an other ideas, or can it only really be the lamp now? Could a lamp failure be intermittent like this?

Thanks.

[GoNz0]

check theres voltage going in and out the inverter, if there is then it could be the lamp, or even the lid switch !

[Agent]

It sounds like the switch is playing up - its easy to test with a multimeter

[Jodo]

Okay, now I'm going to look a right dope. ....I've never used a multimeter before but I can get hold of one easily right now. Anyone have a good link for a crash course?

If I posted a pic of the switch, would one of you guys be able to tell me how to go about it. Or am I best taking it in to a shop for repair? (I would rather learn how to use a multimeter though!!)

Thanks guys

[GoNz0]

use dc volatage to check the cable going from the laptop to the inverter, start at the 12v and if it hits a solid 1 up the multimeter to 120-240v and check again (you wont blow it up)

the output to the lamp should be AC, same again start low and step up if it hits 1

[Agent]

Easier way - set the Multimeter to continuity / resistance mode.
Put one side on the switch input, and the other on the output. Toggle the switch and it should change when being pressed.

If it changes when you're not pressing it, you've got your issue

[GravityTheDon]

Could possibly be the cable. Does the backlight go off & on when the cable is manipulated at all?

[Jodo]

Just had a chance to test this (way too busy at the moment !)

Right, did as you said Agent, placed one side on the input wire, the other on the output.

Display went from 1 to 000 then after a few seconds up to about 1200, moved around a bit, went to -514 (ish) then back to 000 and repeated every few secs (all without me toggling the lid switch). It also changes when I toggle the switch.

So I guess that it IS the switch that is knackered ?

Only problem now is getting a replacement. I can see the plastic toggle bit on eBay, but none of the electrics to go with it

[GoNz0]

remove said switch and bridge the wires, cheap repair but the laptop wont respond to the lid being closed. at least it will tell you for sure if thats the issue