Thinkpads Forum

Hi,
I have a T400 that has a LCD problem, the simtoms are:
- you can see the LCD is working(booting to windows), but without brightness, as it has no backlight
- all the green LED indicators does not work, on the WiFi and Bluetooth works

The T400 is out of warranty, and I'm weighting my options.

Should I buy a new inverter, cable or LCD panel? Is there a easy way to find out
what component failed(inverter, cable, panel)?

Many thanks
Oliver

Admin edit: Added PICS warning.

Maybe as a first step, hook it up to an external screen to see if it works.

oliversl wrote:Hi,
I have a T400 that has a LCD problem, the simtoms are:
- you can see the LCD is working(booting to windows), but without brightness, as it has no backlight
- all the green LED indicators does not work, on the WiFi and Bluetooth works

The T400 is out of warranty, and I'm weighting my options.

Should I buy a new inverter, cable or LCD panel? Is there a easy way to find out
what component failed(inverter, cable, panel)?

Many thanks
Oliver

I would try inverter first since they are so cheap, but it is very likely to be the screen. If your T400 has the 1280x800 screen, it would be a great time to upgrade the 1440x900.

Thanks Zaz and Jayton,
I can see that the screen is working fine. It just does not have any backlight.

Will try to purchase an inverter and report back.

Regards,
Oliver

Hi,

@oliversl, have you reseated your inverter ?

I've got the same problem as you and i do not know what to change, the inverter or cable.

P.S How can i check what type of backlight do i have ? It's lcd.
P.S 2 What does these numbers mean (6475-CTO, 21x, 22x) ?

Will try that first! Thanks

Oliver

hubold wrote:Hi,

@oliversl, have you reseated your inverter ?

I've got the same problem as you and i do not know what to change, the inverter or cable.

P.S How can i check what type of backlight do i have ? It's lcd.
P.S 2 What does these numbers mean (6475-CTO, 21x, 22x) ?

How its working ?

The T400 may be in warranty, so I stopped just before opening the screen. Will report back in about a week.

I've bought an inverter. I'm wondering if inverter is bad or smth in my computer is bad , becouse its not working with this other one inverter. Got some idea ? Anyone ?

I have done the resetting and still no backlight.

Will try to test with another inverter from another T400. If that works, then I will buy the inverter. The PN is:
FRU PN 42W8231

Any link for buying Lenovo parts?

Thanks
Oliver

hubold wrote:I've bought an inverter. I'm wondering if inverter is bad or smth in my computer is bad , becouse its not working with this other one inverter. Got some idea ? Anyone ?

Can you see the image on the screen? but without backlight? Where did you buy the inverter? Thanks
Oliver

hubold wrote:I've bought an inverter. I'm wondering if inverter is bad or smth in my computer is bad , becouse its not working with this other one inverter. Got some idea ? Anyone ?

I can barely see. I bought the inverter on the web site like an ebay but polish one.

If there is no backlight, you have a few options:
1) the backlight-fuse on the motherboard is faulty (happens sometimes)
2) the inverter is faulty (rarely)
3) the CCFL-tube is faulty or broken/burnt through (most often the problem).
Any reddish tint of the screen before this happened?
CCFL can be replaced (or replace the LCD-panel itself, or replace the complete lid)

1) the backlight-fuse on the motherboard is faulty (happens sometimes)

I had an LED LCD T400 with this issue, sounds like the OP's issue, too. I had to replace the mobo. That was after trying a brand new LED LCD!

The fuse is more likely to blow on LED backlights because there is no inverter. The screen runs off DC which goes direct from the motherboard. With CCFL backlight, the inverter (converts DC to AC) blows. Sometimes, it is a fuse on the inverter, but they are cheap enough that it isn't worth changing.

Well, I bought the:
FRU PN 42W8231

and the problem is not solved. Should I buy a new LCD screen or could it be something on the motherboard.

I experienced not reddish color before failing.

Thanks
Oliver

oliversl wrote:I have done the resetting and still no backlight.

Will try to test with another inverter from another T400. If that works, then I will buy the inverter. The PN is:
FRU PN 42W8231

Any link for buying Lenovo parts?

Thanks
Oliver

oliversl wrote:Well, I bought the:
FRU PN 42W8231

and the problem is not solved. Should I buy a new LCD screen or could it be something on the motherboard.

I experienced not reddish color before failing.

Thanks
Oliver

That would be my next step if it were me. Screens are pretty cheap on ebay here in the U.S. It might cost a little more to ship one down there to paradise.

Thanks Jayton, will search for the part. If I only had the resources to enjoy the paradise ...

BTW, my LCD is FRU PN # 27R2412, made by Samsung.

Will search for that part on ebay, if anyone knows a good store I will apreciate it.

Regards,
Oliver

underclocker wrote:I had an LED LCD T400 with this issue, sounds like the OP's issue, too. I had to replace the mobo. That was after trying a brand new LED LCD!

When having faulty backlight fuse on the motherboard, would I still get images when connected to a external monitor?

I'm trying to help my friend fixing his T400 which has exact problem :
1. Black screen.
2. green LED indicators does not work except for wifi.
3. When plug in an external monitor, I can see the screen ( which, I think, tells me that video card is working ).

This narrows down to the LED panel ( or just the backlight ), or blown fuse I guess.

With a blown fuse, an external monitor would work fine. Your symptoms would be no backlight on the LCD and often missing indicators on the bottom of the screen, depending on whether you have one or two fuses out.

Tony Chan wrote: This narrows down to the LED panel ( or just the backlight ), or blown fuse I guess.

I would add a loose cable to the list of possibilities in your situation. Are you using Windows as your OS? While connected to the external monitor, do the display properties allow you to extend to both displays or is the external display the only one that it registers?

richk wrote:With a blown fuse, an external monitor would work fine. Your symptoms would be no backlight on the LCD and often missing indicators on the bottom of the screen, depending on whether you have one or two fuses out.

That seems to be the exact sympton.

jayton4 wrote:I would add a loose cable to the list of possibilities in your situation. Are you using Windows as your OS? While connected to the external monitor, do the display properties allow you to extend to both displays or is the external display the only one that it registers?

I just connected a external monitor and only 1 display option ( the external monitor I just connected ) show up. What does this mean? that I might have a loose cable?

Btw, thanks for the quick responses. Really appreciated.

Just an update from my part. I managed to get an authorized technical support to take a look a the T400.

They say they need to replace: LCD screen, LCD cable and motherboard. So, I don't know exactly what failed and why, but since they are changing the motherboard, I think my problem was the fuse on the motherboard Tony told us about.

HTH
Oliver

It was under warranty?

Warranty just expired for few months.

Was under 3years onsite and motherboard was changed onsite a year ago because of shot usb port.

The technician disassemble the laptop, swapped the motherboard, and re-assembled everything within 45 minutes!

This really doesn't sound good. Oliver, did you see only one monitor when you have blank screen?

Hi Tony,
the T400 works perfect, no problem other than "no backlight on LCD" and "no green LEDs under the LCD".

Regards,
Oliver

Tony Chan wrote:Warranty just expired for few months.

Was under 3years onsite and motherboard was changed onsite a year ago because of shot usb port.

The technician disassemble the laptop, swapped the motherboard, and re-assembled everything within 45 minutes!

This really doesn't sound good. Oliver, did you see only one monitor when you have blank screen?

hi friends

I have same problem in my laptop type lenovo R400
it is work normal but the backlight it is not work
led under the LCD not work except bluetooth led

if you have help to solve this problem

thanks

hi friends

I have same problem in my laptop type lenovo R400
it is work normal but the backlight it is not work
led under the LCD not work except bluetooth led

if you have help to solve this problem

thanks

With the Bluetooth light working and no others, I assume 1 or 2 blown fuses on the motherboard. (They are near the LCD connector. There is a larger one with a "P" on it, and a smaller one that usually has an "F" on it.

Had the same problem and it's solved now. I found the solution somewhere else and I couldn't locate the same now, so I'll add my screenshots and case now
In this case, the lcd backlight and indicator lights are not working, except the wifi led (leftmost the indicator lights row), if you connect your laptop to an external monitor you'll have an output.
The problem here is that no power is reaching the display section, usually for one of two reasons:
* Either the LCD cable is damaged (the power line(s) of the cable connecting the mobo to the LCD are cut), this case you'll need to replace the cable (my LCD cable model is 93P4593, it's similar to the one in http://goo.gl/iQ9Ze9).
* Or it's just a fuse that needs to be replaced or jumped, this was the problem of my T400. Here's what I did:
1) Remove the palmrest and keyboard
2) locate the display cable connection to the motherboard (mobo), you'll need to remove one screw which fixes the cable to the mobo.
3) locate the two fuses, marked in red ellipses in the following image. The fuses are very tiny, their lengths are around 1.5ml and 0.5ml, found just under the aluminium chassis/frame. The photo is taken from above the screen which was laid back 180 degrees.

4) Replace (safer, but needs an expert service) or jump (as a last solution) the fuses. I jumped them using a "conductive wire glue", like the one found in http://goo.gl/VFQBsz. The fuses are not so easy to access, I used the needle provided with the conductive wire glue syringe. Here's the result:

5) Assembled everything, waited 8 hours to make sure the glue dried, switched on my laptop and the LCD and leds were totally working.
Hope this helps somebody out there.