Lenovo ThinkPad Edge E420s wont turn on, won’t power on, no display, black screen problems

Laptop Lenovo ThinkPad Edge E420s won’t turn on, won’t power on, there is no display, just a black screen. This is a general diagnostic and repair steps to fix those problems.

Troubleshooting laptop Lenovo ThinkPad Edge E420s won’t boot, won’t power on, no display just black screen

When you push on the Power Button the Power led lights ON or NOT, your Lenovo ThinkPad Edge E420s won’t start up, and there is no display just a black screen. Possible problem and the fixes steps:

Battery has no charge left + AC adapter failed; you press the power button on laptop Lenovo ThinkPad Edge E420s nothing happens, laptop won’t turns on and there is no display, the battery has no charge left, the motherboard doesn’t receive any power, laptop cannot turn on. You plug in the AC adapter but that doesn’t help, your laptop Lenovo ThinkPad Edge E420s still won’t power on, there is a chance you have failed AC adapter. In this case try with another charger or check AC adapter with a Multimeter. If it’s dead, replaced with a new one.

Power circuit in wrong state or Over volt protection trips; you press the power button but nothing happens, laptop Lenovo ThinkPad Edge E420s won’t turns on and there is no display just a black screen, your laptop has static electric charge made power circuit in wrong state. Unplug AC adapter, take out the battery and hold down power button for 30 seconds, the static charge will dissipate. Plug in the AC Adapter and turn on your laptop Lenovo ThinkPad Edge E420s. This should restore the system to normal operating mode.

Hardware failure; the laptop powers on, but there is no display just black screen with Power led lights ON or your laptop Lenovo ThinkPad Edge E420s stock on logo or restart. In this case, it’s possible one of the Hardware failed. You can try to disassemble the laptop to bare minimum and try to reseat the hardware one by one and power on the laptop every time you reseat a hardware, to know the failed one, replace the faulty hardware.

Screen faulty or bad video cable connection; laptop Lenovo ThinkPad Edge E420s turns on, but screen is black, with Power led lights ON. Test the laptop with an external monitor connected to the HDMI port, VGA port, press the appropriate key to switch to it. If the external monitor works fine and load the operation system, most likely you have a faulty screen or bad video cable connection. Check them and replace the faulty one.

BIOS failed; Laptop Lenovo ThinkPad Edge E420s won’t turn on at all, if the voltage 19V, 3.3V, 5V OK  and electronics components on the motherboard are good, there is chance you have failed BIOS. There is a signal test confirmation on EC/SIO pin name RSMRST# . This pin must available 3.3V(tolerance 10%) than Bios Confirmed OK. If the test failed reprogram or replace the BIOS chip.

Laptop Power System has problem: Laptop Lenovo ThinkPad Edge E420s won’t turn on at all, probably some electronics components or chipset on the motherboard failed;  Disassemble the laptop and take out the motherboard. Ceck No burnt marks visible on the mainboard. Check chepset temperature (CPU,  GPU, Power-Supply IC …). Check power jack. Check motherboard receives 19V. with a Multimeter measure voltages on coils, check for any components shorted to ground.  checked 3.3v/5v is up and running?

If you  have 3VALW And 5VALW at coil. 3VALW should go to sio and from there you should get 3v at power button. Check SIO for corrosion,shorting or any componenets which looks suspect. Check 3 & 5v SUS voltage.

Will need an electronic boardview or Schematic Diagram for Laptop Lenovo ThinkPad Edge E420s. The failed electronic component has to be replaced.

Note: (In the comments we will be updated electronics components failure).

Motherboard dead; The Lenovo ThinkPad Edge E420s motherboard has to be replaced.

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For other Lenovo ThinkPad Edge E420s problems check the comments or write a comment.

One thought on “Lenovo ThinkPad Edge E420s wont turn on, won’t power on, no display, black screen problems

  1. active

    Found this on another forum:
    Finally E420s motherboard REVIVED / FIXED / REPAIRED !!!

    After serious efforts and wasting substantial amount of cash and time (and lotsss of reading :smileyhappy:…. ) I have managed to revive my Lenovo E420s motherboard . Even I have contacted WISTRON company the one designing and manufacturing the MB for LENOVO. I asked them for the electrical schematic for this MB but as you can guess NO SUCCESS.

    On my previous posts I have asked if there are folks who want to sell their faulty motherboards and the reason was simple, wanted to test and see if they have the same issue but………. no one was interested in selling faulty E420s MB.

    Here are the specs of my Lenovo E420s:
    CPU: Intel iCore 5 2nd generation
    RAM: 16GB, 2 x 8GB
    Video: Intel 3000HD
    SSD: 64GB msata, MyDigitalDiscount BulletProof
    HDD: 500GB, Hitachi 7mm, 5400rpm
    2nd HDD: SATA caddy with 1TB 9.5mm (DVD was replaced with an HDD caddy)

    Anyway, let us get to the problem first and then to the solution:

    – PROBLEM (the one that I had)

    Whilst the laptop was perfectly working it suddenly powered/went off for no reason (the same as you pull the power cord from a DESKTOP PC). When I tried to power up, the first couple of times of pushing the power button did not work but I was persistent and after of couple of more pushes the laptop powered up, lucky me :smileyhappy:. The interesting thing here was LENOVO power management gauge (green battery gauge on the bottom right corner next to system tray) was indicating that laptop is connected to the power adapter but the battery was draining/discharging. I was just watching how the battery is depleting till it was fully empty and the laptop went off and never powered up again.
    There was no indication at all for anything – NO RED LIGHT on the dot of “i” and the green LED next to the power jack was off even though the power adapter was connected to the laptop. BTW this green LED indicates if your laptop is charging the battery.

    here i am gonna skip the all the non senses that i have done in order to get my laptop working again and go straight for the solution. All the images (only 3 images :smileywink: ) are uploaded on my dropbox and you can download them from there.

    Here is the link: https://www.dropbox.com/sh/3o1njwwgvfjho2n/ma8fpW7wKt

    – Solution:

    1. You have to disassemble the laptop and to take out the system board or for shortly MB.
    Please remove all the components from the MB. You have to end up only with bare MB with components which are soldered on it. you can keep the cpu and gpu and the cooling assembly on. Refer to the image named top_MB_e420s.jpg

    2. On the bottom side of the MB there is one connector with 5 pins which provides the POWER for the MB. The cable connected to this connector is coming from the POWER JACK of the laptop in our case this is the 20V voltage power source from the power adapter. Have a look at image bottom_MB_e420s.jpg the yellow square.

    3. NEXT to this connector there are 2 small chips with 8 pins. These 2 chips are MOSFET transistors (both of them are same part number) and they are acting as a SWITCH or with other words as a POWER SOURCE SELECTOR. To visualize how these 2 MOSFETs are connected have a look at Fig.1 on this webpage: “http://www.eetimes.com/design/power-management-design/4012528/Fundamentals-of-designing-with-MOSFET-…”. No harm will be done if you want to read the whole article as well. Please check image named “bottom_MB_e420s.jpg” red rectangular.

    4. After measuring these 2 MOSFETs with multimeter I have established that one of them was gone / faulty. Here is the MOSFETs part number: FDS6675BZ – this is P-channel 30V 11A. You can get 6pcs from ebay for only USD 3-4.
    Here I would recommend to replace both MOSFETs. DO NOT replace only the faulty one. For more information you can refer to the datasheet of the MOSFET. Refer to image named “bottom_MB_e420s.jpg” for locating the MOSFETs.


    So for my case scenario these MOSFETs were the problem by replacing them everything worked just fine with no problem at all. I left the laptop running for 48 hours no problem observed, I have restarted it couple of times with no issues as well and reinstalled the OS.

    I have another faulty E420s MB and the MOSFETs there are with the following part numbers: AO4407A. As you can guess the problem with this MB is the same – one of the MOSFETs is gone. This MOSFET is identical to the above mentioned and you can interchange this one with the above mentioned MOSFET. Please refer to the datasheet to check the most important parameters Id, Vd, Rds.
    This MB have not fixed yet due to blowing a small SMD resistor 0.01ohm ohm and now I cannot find this SMD resistor. I f you can help me find this resistor from somewhere will appreciate very much.

    On my dropbox public folder I have uploaded the location of the BIOS chip as well. It is only for your information.

    So, I hope this will help most of you to revive your Lenovo E420s laptop and start using it again.

    If this info helped you to revive your e420s I will appreciate your donation to recover some of the cash that i have wasted to repair this MB.

    you can donate to my paypal here is the email:xxxxxxxxxxxxxxxx

    If you have any questions feel free to contact me on the same email will try my best to help you all.

    Thank you!

    And Good Luck!
    E420s dead motherboard revived fixed repaired!!!

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