cancel
Showing results for 
Search instead for 
Did you mean: 
Reply
Reforminded
Punch Card
Posts: 10
Registered: ‎10-30-2018
Location: US
Views: 109
Message 11 of 15

Re: T400 Display crapped out - help with FRU's

To add some more discoveries to the ongoing problem, I have two new bits of information.  First, I noticed that the screen doesn't go completely black until it gets past the bios and goes into windows (I can faintly see the splash screen and bios menus, better if I hold a light up to it--but it goes out completely if I go into windows).  I decided to test another OS to see if Windows might be the problem, so I created an Unbunto boot stick and booted off that.  It had the same symptoms--I could faintly see the Unbuntu spalsh screen, then also the boot menu asking if I wanted to "try" or "install".  When I selected "try", as it started to boot Unbuntu the screen went completly black. As with windows, I plugged in an external monitor and it worked fine.  On this same point, neither Windows nor Unbuntu can recognize the internal monitor, only the external (both OS' only see one monitor attached to the computer).  This last part is weird to me since the laptop's screen is (faintly) displaying at startup. 

 

The second thing I observed today, was that if I move the lid back (further open) it causes the screen to flicker and cut out.  I can specifically replicate it my flexing the lower left hinge area.  I am perplexed by this, as the main LED cable is nowhere close to this and I thought it was just some antennas running through that part. 

 

Does anybody have any ideas?  I know the LED cable isn't being pinched or pulled and I know it is seated as I just replaced it again.

Reforminded
Punch Card
Posts: 10
Registered: ‎10-30-2018
Location: US
Views: 86
Message 12 of 15

Re: T400 Display crapped out - help with FRU's

Does anyone out there have any ideas on this situation?  Would really like to find a way to fix it.

Reforminded
Punch Card
Posts: 10
Registered: ‎10-30-2018
Location: US
Views: 48
Message 13 of 15

Re: T400 Display crapped out - help with FRU's

Found the solution for anyone else with a T400 that has the dim screen issue.  Despite the advice given here, the display panel was fine, the cable was fine, the inverter/LCD control panel was fine.  And the motherboards were fine until they got installed in my system and had a fuse blown--BY THE BLUETOOTH CARD.  The bluetooth cards in these systems are crap and die early, then they short out the fuse on the motherboard that powers the display backlight.  I got another motherboard, removed the bluetooth card, and put everything back together with the original screen and cable and everything is working like new. 

 

Again, for anyone with a T400 with a dim (almost blacked out) display issue, do not waste your time or money following the advice others have given here by chasing screens and cables.  Just remove the bluetooth and replace the motherboard (or fix the blown fuse).  If you leave the crappy bluetooth in it will just immediately short out the new motherboard.

Community SeniorMod
Community SeniorMod
Posts: 10,054
Registered: ‎01-01-2010
Location: US
Views: 42
Message 14 of 15

Re: T400 Display crapped out - help with FRU's

More possibilities.  Do you have an LED backlight or CCFL?  T400 had both options.  If CCFL, it could be the inverter.  It could be the Hall sensor (lid-closed switch).  If you changed the motherboard before the screen and the old screen was shorted, you could have blown another fuse.


Rich


I do not respond to requests for private, one-on-one help. Your questions should be posted in the appropriate forum where they may help others as well.

If a response answers your question, please mark it as the accepted solution.

I am not an employee or agent of Lenovo.
Reforminded
Punch Card
Posts: 10
Registered: ‎10-30-2018
Location: US
Views: 25
Message 15 of 15

Re: T400 Display crapped out - help with FRU's

Perhaps you didn't read my follow up post? It was the bluetooth module (which runs through the same fuses on the MB) shorting out the fuse. As stated earlier, I have an LED. The cable was fine, the hall sensor was fine, old screen was fine, everything else was fine. It was a crappy bluetooth module shorting out the MB fuse, which is the same fuse that that controls the indicator lights and display backlight. In this case, it was your poor advice that sent me on a wild goose chase and cost me lots of money. The bluetooth module is a known issue that for some reason was never discussed on this board. Remove bluetooth and repair fuse (or replace MB) and everything is good as new.

Check out current deals!


Shop current deals

Top Kudoed Authors