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The Lenovo Thinkpad X240, released in 2013, fairly light and compact, and looks familiar to the ThinkPad Line. The X240 is notable for its clunky touch pad.

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Why is my Lenovo Thinkpad X240 Screen Black?

I found a decent deal on a Lenovo X240 and found it had no HD and no memory. I found online the specifications for the memory and ordered the “Crucial 8GB (1x8GB) DDR3 RAM 1600MHz PC3L-12800 laptop Memory CT102464BF160B” for and installed a 256GB Samsung SSD drive I had already.

Since I don’t have a power supply with the plug needed, I found Lenovo makes an adapter for the older yellow style barrel plugs and ordered one of those and just received.

I plugged in the laptop with the 135W 20V Lenovo power supply and all I saw is the green LED turn on at the power button and the keyboard backlight flashes once and sounds like the fan is turning. The Fn LED flashes once green and stays green for about 4 seconds and then stays off. The red LED on the top of the screen “I” in Thinkpad stays lit red.

I did the same with the 90W 20V Lenovo power supply though noticed the red LED on the top of the screen “I” in Thinkpad blinked red 3 times when plugging in the power supply and not even powering on or doing anything else.

I just tested without the power supply plugged in and the same effect as with the 135W power supply… only with the external and internal battery.

Prior to plugging in, the power supply… the battery was dead and the laptop did nothing. I’m guessing one of the chargers must have charged one or both of the batteries somewhat.

Finally, I tried to plug in an external known working monitor with no difference when I cycled power.

The screen is black and never does anything in all the scenarios. What are your thoughts?

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thanks for the this beautiful blog


Your welcome. Thank you.


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The LCD screen backlight is bad for some reason.

Whether LCD assembly, BIOS corrupted to not turn on backlight or a fault on the System Board… I am not sure. If anyone has a schematic for the i7 boards for the X240 or any ideas regarding how to repair without replacing the LCD assembly, please feel free to comment.

Thanks everyone for your support!

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Hi @jafinch78,

Check if there are any fuses on the motherboard around the area where the LCD cable is connected.

Found the following info from this link with regard to a X220 which has a separate backlight cable and an LCD cable and not just the one LCD cable where the backlight power is incorporated into the one cable but perhaps it may be nearly the same. Worth a look ;-)

"There is generally a .5 amp fuse (marked with an "F" on the fuse.). There is also a 2 amp ("N") or 3 amp ("P")."


Hi @jayeff ,


That's more like what I was suspecting. Working with free LED TV's to practice repairing on; I've found the issue is typically bad LED's, then maybe the power supply, then maybe the inverter, then maybe somewhere on the controller board. Logically, thinking about on the Laptop systems and looking more thoroughly into the components level of thinking... the link you noted was the direction I was thinking also since if not a common modular part... the process is designed into the motherboard since instead of being an MCU is a SBC.

Glad this is posted for later reference. I'm going to take a break on this project for a few days or so as I have outdoor work to do. I'll try to make a video regarding also when I find the time to work on. Thanks again!


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Hi @jafinch78 ,

Try disconnecting both the internal and external batteries and see if it starts just on the AC power.

Here’s a link to the service manual for the laptop.

Scroll to the bottom of p.60 to view the necessary pre-requisite steps and then the procedure to remove the internal battery. You should only have to disconnect it, not actually remove it.

The manual also mentions an Emergency reset button hole in the Power system checkout on p.26 which you may have to operate as well to get things started.

Also try removing the coin cell battery p.73 for a while (15-20 minutes - can’t find RTC reset pins) to allow it to get back to default BIOS settings in case they’re corrupted. (Check its’ voltage as well as it may also be flat and if it is as it non rechargeable it will have to be replaced).

If you remove the RAM and the SSD does it behave differently when trying to start?

If you can’t get it going at all, what was its’ working condition described as, when you bought it? Working but missing parts etc or “As is”, because if it’s a faulty systemboard you may have problems...

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Here is the info on the reset button:

The link got me thinking to shine a flashlight into the LCD to see if that is working in case the backlight isn't working for some reason like burnt out, inverter or in the scenario where I made a Repair Guide regarding the A70z Thinkcentre regarding and issue I never saw before: Lenovo ThinkCentre A70z Backlight Cable Replacement

So far removing the batteries has done nothing new, same goes with holding down the emergency reset button for 15 seconds.

I am about to remove the internal battery to get to the CMOS battery and see what that does.

I did however after thinking about the backlight issue above shine a light at the LCD and notice that the "Thinkpad" slash screen is appearing. That's good.

Hopefully, resetting the CMOS will turn the backlight on properly since I doubt the inverter for the backlight is a separate module.


Hi @jafinch78 ,

Not sure but there may also be a lid switch (magnetic - magnet in lid and switch in case or vise versa) which controls the power to the backlight i.e. turns off the backlight power when the lid is closed, which may be faulty.

Either the power is routed through the switch OR the switch sends a signal to the BIOS to enable/disable the power. If the latter usually the switch is somewhere around the Power button. Just a thought.


Both internal and external batteries aren't showing any power which is strange since I was able to power up without the power supply. I do see the 135W power supply for some reason sparked when I just plugged in to the surge protector and now is only reading 8.62V. Wondering if that did something strange since is the PS that came with the laptop... maybe something to do with why that power supply, when plugging in only, made the letter "i" on the cover blink three times?

The other PS is reading 20V though is only 90W. Not sure if related at all or not.

I'll just unplugged the CMOS and will let sit for a while before connecting everything again.

Reading into some more regarding the backlight I found these threads:


Hi @jayeff,

Good call regarding the switch. I'll have to read into that some more. Any references by chance? I guess that makes sense why the external monitor isn't working.


There is a blue and an orange wire ending where the WAN/M.2 SSD card can go (is note used on this system). I guess from the looks of the system, those wires are the WAN antennas. Wow, do those have small RF connectors.

Well, I plugged back in the CMOS battery and now get two beeps... though every other process appears the same as found.

Will check the memory and the SSD when removed next.

Wondering if the "fuse" on the motherboard is bad. I'm not sure the magnetic switch concept is wrong and thinking about hacking that to look like the lid is open as an easier attempt. I guess if that has pinouts that are accessible, see what the state looks like and do the opposite.


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I didn’t want to answer this, but there is some potentially dangerous information in the previous answer you best not follow yet until you know if it has an SVP.

Before you do ANYTHING with the system (especially the CMOS battery), get a external display that has VGA if at all possible; it can be DVI/HDMI only, but you will need a mDP adapter like this to get it going as the Thinkpad only has onboard VGA. We’ll get to why I want you to mess with literally anything else before the CMOS battery. It doesn’t need to be a new monitor - something used from a thrift store will work as long as it has the ports you need.

Removing the CMOS battery on a Thinkpad 390E-XX30 is a potentially dangerous mistake; if you can recover the ATMEL chip, you can oops it. However, it is DEADLY on the XX40-present generation with Boot Guard. If you reset the ATMEL chip using the old methods, you will lock the machine out due to tampering and need a motherboard. If you removed it without being sure, this is a deadly error if you had a SVP :(. If I’m reading the previous thread right, pray it never came with a SVP.

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There is a Analog VGA output on the X240 I have. I am going to set the Display settings to Analog VGA in BIOS and try that next.


99% of thrift store monitors have VGA so it'll work if you have a known good cable and monitor.

I was really hoping I didn't see the part where you tested it and potentially removed it.


Do you happen to know if the inverter for the backlight is in the LCD module/assembly or on the motherboard?

I'm wondering if the inverter is bad or too many LED's burnt out.

I didn't see a backlight setting in BIOS as I read some laptops have I guess.


LED monitors don't use a backlight. They are driven from the motherboard, so if a known good panel doesn't work you need to repair the motherboard.



I think the monitor LCD's use backlights though around the perimeter of the screen in some designs versus directly behind. I can see the screen display on the X240 when I shine a LED light at certain angles so I know the LCD screen part of the display is working... not the backlight. I'm pretty sure this is correct. Please reference otherwise since would be new to me. I even have a Lenovo A70z LCD monitor repair regarding the backlight with a known issue on iFixit. You can check out my guides for more info.


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