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W500 Backlight Issues

W500/510/520 and W700/710 series specific matters only
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seahuston
Posts: 1
Joined: Wed Feb 20, 2013 9:24 am
Location: Newmarket, NH

W500 Backlight Issues

#1 Post by seahuston » Wed Feb 20, 2013 9:38 am

Hi All,
Looking for some help here as I am running out of options and need to get my laptop working.
ISSUE:
Backlight on my W500 does not work. If I look closesly, I can see the thinkpad text when I start up the laptop so the display appears to be working.
SYMPTOMS/DEVELOPMENT:
The issues started that if I tapped or jiggled the screen it would blink out black. It eventually became worse and then finally just never would light up. External monitor still works.
CURRENT PROGRESS:
Replaced backlight: Did very little testing and thought the backlight was the issue. I replaced the backlight and the issue was not resolved. I know the backlight was replaced properly because I can plug it into my T61 and the light turns on.
Replaced Inverter: Next step down the rabbit hole. I ordered a new inverter and replaced the old one. Still, no dice. I didn't test this new inverter but the LED lights on it work.
Replaced Display Cable: This seemed logical given the fact that tapping the screen caused the issue at first. Still, no dice. I just tried this step and didn't fully assemble the laptop before turning it on. Thinking that maybe the screen open sensor is located on a chip I didn't put back on yet. Still, the thinkpad startup screen can be seen if I look closely.

NEXT STEPS:
Looking for help here.
I'm thinking that maybe the lid sensor is bad. Is this possible and would that make sense if I can still see the display even with the backlight off.
Fuses? It seems like the initial tapping would indicate that it isn't a fuse issue but maybe it is. Can someone point me in the direction of the fuses to test?
Any other thoughts?

Thank you all so much. I hope this gets resolved.

Zak
Sophomore Member
Posts: 140
Joined: Wed Sep 21, 2005 8:57 am

Re: W500 Backlight Issues

#2 Post by Zak » Wed Mar 13, 2013 1:09 pm

I'm pretty sure screen blanking on lid close will both turn off the backlight and blank the image. If you run Linux or want to check that using a Linux boot disk, cat /proc/acpi/button/lid/LID/state to see whether the machine thinks the lid is open. There's probably also some way to tell on Windows, but I don't know what it is.

berrieds
Posts: 13
Joined: Fri Nov 20, 2015 3:29 pm
Location: Manchester, UK

Re: W500 Backlight Issues

#3 Post by berrieds » Sat Feb 01, 2020 8:18 am

W500 backlight [solved] - in my case at least.

I have had this same issue, and, after taking the laptop apart and doing some testing, I found that the F8 fuse was busted. This powers the inverter, and controls some of the backlight control. If HDD and WiFi indicators etc. are all lighting up properly, then it might be an issue with the F7 fuse, which was fine on my board.

I had a spare, non-working board to pull a fuse from, but they probably can be picked up quite cheap. F8 is really tiny, 0.5A, and really fiddly, but you can solder the fuse right onto existing one, without trying to remove the fuse that's already there (and potentially damaging other components in the area), soldering iron temperature at 315 °C seemed to work alright. If it is too high, you can easily fry the fuse.

There are some schematics and photos on the thinkwiki.de site that have been helpful to identify parts. Posting this here because even years later I have run into this problem, and was looking for the right solution. Hopefully if you've fond this then it might help you too.

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