Replaced all possible parts and still no backlight :(

sharingan_sasuk · 6 Jun 2011 at 17:54

Hi all, I have a IBM Lenovo T500 laptop from the United States that was dropped and resulted in a cracked panel. I bought a new panel and installed it and while I could see the desktop at a certain angle, there was absolutely no backlighting at all, even when using the fn keys to max out the brightness.

It outputs fine via VGA to an external monitor.

I double checked the LCD panel cable and found a small copper connection snapped off, so I ordered a new cable thinking that would solve the issue. Again, no backlight.

So I thought surely it must be the inverter which I ordered and installed. Again, still no backlight!

I'm guessing it must be the motherboard now which could have been damaged when it was dropped. In which case, I won't want to spend anymore money fixing this. But if the motherboard is damaged, then why would it still output fine on an external monitor?

Does anyone have any more ideas cos I've run out of them

Many thanks.

Surveyor · 6 Jun 2011 at 18:33

Did the new panel include the backlight bulbs, or whatever they're called.

RJC · 6 Jun 2011 at 18:37

It could be the cold cathode tube has failed / or is broken when dropped.

Some of out plant were I work use Sharp LCD screens to display there status and I so far we have replace 2 screens complete and I have changed the back light for two of them.

Surveyor · 6 Jun 2011 at 19:14

RJC said:
It could be the cold cathode tube has failed / or is broken when dropped.

I think that's what I was trying to say

I know bugger all about laptops.

RJC · 6 Jun 2011 at 19:18

Surveyor said:
I think that's what I was trying to say

I know bugger all about laptops.

I know minimal amount after my Dell Laptop decided to fail, taking the screens apart at work helped, back light slides along the top with a reflector, surprised how hot they got, managed to melt the plastic!

Screen below:

sharingan_sasuk · 6 Jun 2011 at 19:54

I've opened up this laptop so many times and I don't believe there is a bulb anywhere else other than in the panel itself, and I've already installed a new one. Assuming that the new panel is fine, then my guess would be it's not the bulb. As I don't have easy access to parts as this laptop is from the United States, ordering a new panel, cable or inverter again is out of the question as this would be dragging it on for longer than anticipated and I may as well just send it back to Lenovo themselves

I'm sure I have replaced pretty much everything I can in the LCD frame and if I'm still getting backlight issues, then it must be something else in the lower half underneath the keyboard right. If I can just confirm it's a motherboard, then that will end this case once and for all as we may as well get a new laptop.

LaRZ · 6 Jun 2011 at 20:58

Sometimes the backlight can die but the panel itself is still working, you can faintly see that the LCD crystals are still displaying what they should, but only under a good light source.

It sounds as though the laptop has encountered more damage than just a damaged backlight though.

I'd suggest you send it off to IMB to have the whole display replaced.

Either that or live with only being able to use it on an external display.

spleenharvester · 6 Jun 2011 at 21:01

If all the connections are right, deffo sounds like something's gone on the board.

panyan · 6 Jun 2011 at 21:05

LaRZ said:
Sometimes the backlight can die but the panel itself is still working, you can faintly see that the LCD crystals are still displaying what they should, but only under a good light source.

+1

sharingan_sasuk · 6 Jun 2011 at 21:17

Well in the LCD assembly itself, all you have is the panel, cable and inverter. So I assume the backlight is part of the panel itself, which has already been replaced with a new one. So I don't think replacing any part of the LCD assembly will make a difference.

I think I'll just take the IBM advice and let them diagnose it. I have done all I can with limited access to parts!

LaRZ · 6 Jun 2011 at 21:21

You have been bolder than I would have, to try and replace the panel/ components.

If you say the new panel has been fitted, but has no backlight, (yet you see an image at an angle under good light)

= you either have no power going to the back light of the panel by damaged paths/circuits, or the ccfl backlight you have in your replacement panel is faulty.

sharingan_sasuk · 6 Jun 2011 at 21:37

Replacing each of the 3 parts was easy as I managed to find the service manual from Lenovo themselves. Goes all the way from taking the battery out to removing the panel from the LCD assembly. It's a shame I don't have access to the parts easily or another laptop of the same model because it would have then taken me a day at most to pinpoint where the fault was.

d_brennen · 6 Jun 2011 at 22:18

Not impossible for a new panel to arrive DOA, I've seen this a few times. I've got a couple of faulty screens (have lines/bruises but backlight is fine) about work for this reason