Laptop repair issue

[plexer]

Got my brother in law's laptop here as he was complaining that the screen kept going dark.

 

It's a Packard Bell New90, eurgh I know

 

When I first turned it on the backlight was functioning but some lines at the top of the display were not showing correctly.

 

I replaced the lcd panel yesterday and the full screen is working perfectly but there is no backlight whatsoever I'm a bit peeved to say the least anyone seen this before? I'm thinking lcd display cable but don't want to blindly change more parts.

 

Ben

[Sam_Brown]

Probably the inverter although never had to diagnose it before. We have plenty of spares here to just go changing things willy nilly and see what sticks...

[bondbill2k2]

I've had iffy inverter boards on a couple of laptops in the past if the LCD display cable seems ok I'd change that.

[plexer]

This is an led screen so don't think it has an inverter like you used to have with a ccfl backlight through there's nothing in the chassis the display cable plugs into the motherboard and then into the control board on the back of the screen.

 

Ben

[Sam_Brown]

Silly question but assume all the cables are plugged in fully? I know a few times I've replaced screens only for the cable to only be about 90% in. I've also replaced screens with the battery still in and managed to singe the end of the cables before which led to similar issues like this.

[plexer]

Cable looks absolutely fine, taken top plastics off and motherboard also looks fine.

 

Ben

[mac_shinobi]

Not saying that you did or did not remove all power sources before swapping the screens over but just to confirm did you remove both the battery and mains power cable before doing any screen swapping on the laptop , as per here : Laptop Replacement Screens: Packard Bell Easynote NEW90, NEW95, MS2273, MS2285, PAWF7, PEW91, P5WS0 Screen Replacement

 

If you left the battery installed whilst swapping the screen over you may have done some damage to some of the component .....

[Smed]

ive changed a laptop lcd with the battery still connected! doh! never again!

think it blew a fuse on the mainboard, had to then get that repaired as well!!

[mac_shinobi]

ive changed a laptop lcd with the battery still connected! doh! never again!

think it blew a fuse on the mainboard, had to then get that repaired as well!!

 

I think it is in relation to the circuitry that steps up the voltage / ampage to power the screen and possibly some circuitry on the screen itself as had a Lenovo Engineer blow both and had to replace the system board and the screen a 2nd time around ( at which point he removed all power sources prior to doing any work on the laptop ) and ensured that all connectors were seated firmly

 

On the Lenovo screens they have some very sticky tape to keep the cable / display cable on the back of the screen connected firmly into the connector on the actual back of the screen

 

edit - may be worth while disconnecting all conections relating to the display cable etc and ensuring that they are all seated firmly and stay in place with some strong sticky tape or the likes ??

Edited March 13, 2014 by mac_shinobi

[plexer]

I actually happened to have another packard bell here which uses the exact same screen, so far I've disconnected the original screen from that and hooked up the original screen from the one I'm repairing and that comes on showing the screen fault which is why I changed it in the first place, next will be to test the screen I bought on the laptop that definately works.

 

Ben

[plexer]

Ok to summarise:

 

Tested faulty laptops screen in good laptop, show screen fault which was missing lines at top of display, backlight works.

Tested new screen in good laptop, screen works fine, backlight works.

Tested new screen in faulty laptop, screen works fine, no backlight.

 

Screen cable is firmly connected both ends as I've had the faulty one down to the motherbaord to check.

 

Possible causes, faulty screen cable or more serious motherboard fault.

 

Ben

[difinity]

plexer, how good are you with a multimeter and soldering iron ?

 

LCD panel connector page 22.

new90.pdf

[plexer]

@difinity thanks for that post and whilst I am proficient I'm not going to take a soldering iron to it.

 

Will try a cable first.

 

Ben

[mac_shinobi]

Ok to summarise:

 

Tested faulty laptops screen in good laptop, show screen fault which was missing lines at top of display, backlight works.

Tested new screen in good laptop, screen works fine, backlight works.

Tested new screen in faulty laptop, screen works fine, no backlight.

 

Screen cable is firmly connected both ends as I've had the faulty one down to the motherbaord to check.

 

Possible causes, faulty screen cable or more serious motherboard fault.

 

Ben

 

What about if you try both the new screen and the working screen on the working laptop but with the display cable from the laptop which is faulty to see if that stlil allows both working screens to work with a back light etc

 

If so then I would say its the mobo on the faulty laptop that needs to be switched - unless it is cheaper to be sent off for repair to sort out the power issue as sounds like the screen is not being provided enough power for the back light to work or something along those lines ??

[plexer]

hmm ok so original screen from dodgy laptop works with the same screen fault in working laptop but now fails to do anything in original dodgy laptop yet new screen still works in dodgy laptop albeit with no backlight.

 

Gah thought this would be a simple swap the screen ta very much.

 

Ben

[plexer]

Just stripped faulty laptop to remove lcd cable.

 

Stripped down good laptop to remove lcd cable, motherboard end of cable differen, doh!!!!

 

Put good laptop back together, ran out of screws, lol, someone has had it apart before judging by all the marks on the casing where they levered the hell out of it due to not knowing what they were doing with it.

 

Do I spend £10 on a new lcd cable or not?

 

Ben

[plexer]

Oh and motherboard on the dodgy laptop looks absolutely fine.

 

Ben

[kevin_lane]

Yea I would at least if its £10 and it dont work then you haven't lost a lot really just means he owes you 2 pints lol

[mac_shinobi]

How much is a replacement system board ?

[plexer]

@mac_shinobi around £30 - £35 for a 2nd hand one on ebay

 

Put the new lcd lead in tonight and it's still the same, my next suspect is the screen hall effect sensor that's connected to the power switch and operated by a magnet under the bezel.

 

Ben

[mac_shinobi]

@plexer - You got a link to one of those. Not heard one of those being mentioned before as a cause to issues with the screen

 

I would have thought

 

1) Inverter ( depending on the type of screen and or laptop as may be that the circuitry on the motherboard that deals with stepping up the voltage / ampage to get enough power to the screens back light or just the screen in general ). I know on some laptops they had the inverter as a separate small pcb that the screen connected into such as the dell D630 as per this video :

 

 

2) LCD Cable which you have already tried

 

3) The screens back light has blown or gone dimm so needs a replacement screen

 

If the inverter circuitry is on the motherboard itself then will need a replacement motherboard

 

Obviously any items you replace or any work you do on laptops you need to ensure that the battery and mains cables are dis-connected before doing replacements of any components

 

Think I mentioned the above previously but just saying again

Edited March 29, 2014 by mac_shinobi

[plexer]

Lcd screen so no inverter the new screen is fine.

 

Most laptops either have a micro switch or hall effect sensor to detect when the lid is closed.

 

Ben

[mac_shinobi]

Lcd screen so no inverter the new screen is fine.

 

Most laptops either have a micro switch or hall effect sensor to detect when the lid is closed.

 

Ben

 

That or the FN Key and another key to increase and decrease brightness or switching modes ie single, cloned, external only , extended desktop etc, bios setting to select the default mode and if it uses the laptop screen / docking connector etc etc

 

Might have to use an external monitor and the FN and other key to switch to the external screen to see the bios settings

 

Wondering if its maybe the gpu / graphics chip over heating ?

Edited March 29, 2014 by mac_shinobi

[plexer]

Nothing in the bios just hooked it up to an external monitor, the fn key combinations for brightness etc... though are user controlled every laptop has a hardware method of determining lid position.

 

Ben

[twin--turbo]

So both screens light on another system but not on this system.

 

Certainly sounds like the fuse for the backlight has blown on the motherboard.

 

Rob