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After serious efforts and wasting substantial amount of cash and time (and lotsss of reading ....
) 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 . 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 ) 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 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-man ... r-switches. 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.
PLEASE BE AWARE MOSFETS ARE VERY SENSITIVE TO STATIC ELECTRICITY. IF YOU GOING TO DO DESOLDERING AND SOLDERING BY YOURSELF PLEASE WEAR ANTISTATIC WRIST STRIP or TAKE NECESSARY ANTISTATIC PRECAUTIONS.
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: alper_ismail@hotmail.com alper_ismail (at) hotmail (dot) com
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!
p.s.
I have just added and the hardware service manual from lenovo for e420s. this will help you to disassemble and assemble your laptop.
