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18 Posts

06-02-2011

Australia

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Re: E420 motherboard problems

2013-05-15, 22:36 PM
Sure thing.
Will take some pictures tonight and send them your way.

Cheers.
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11 Posts

12-10-2012

Bulgaria

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Re: E420 motherboard problems

2013-05-20, 8:49 AM

Hi not4us,

 

I have gone through the pictures you send me and the schematic as well. Could you please tell me what is the problem with your laptop? What exactly happened?

 

OK, I have to say that all the component markings/labels on the MB match with the markings/labels on the schematic that you have provided. Components with labels starting with PUxxxx, PQxxxx, PCxxxxx, PLxxxx, PDxxxx are part of the POWER BLOCK of your MB (all related to the power supply block).

 

Unfortunately I could not locate the 2 mosfets from the images you sent me but referring to page_40 from the schematic PU4001 and PU4002 are the mosfets that we are looking for. Please try to find these 2 marking on the MB.

 

PLEASE USE ANTISTATIC PRECAUTIONS OR YOU GONNA BLOW YOUR MOSFETS.

 

About how to measure them: In my case the internal diode connected between DRAIN and SOURCE (you need to check the mosfet datasheet for DRAIN SOURCE and GATE pins) was blown. You can easily measure it with a Multimeter where you should select the DIODE mode on it. If you get SHORTEN CIRCUIT (multimeter beeps or gives you reading of 0) between DRAIN and SOURCE pins then it is gone. More info about measuring MOSFETs please google.

 

PLEASE USE ANTISTATIC PRECAUTIONS OR YOU GONNA BLOW YOUR MOSFETS.

 

Let me give you some more info: IC chip on page_40 labeled PU4003 is the battery charger. Please confirm if you have the same chip on your MB - BQ24745RHDR. What you can do here is to check if you get the INPUT voltage from the power adapter - 20V. Please refer to the datasheet of the chip for the INPUT pin.

 

On page 41 you have the power management IC chip which is labeled PU4103 on your MB - BD95280MUV. Please confirm if you have the same (you gonna need a magnifying glass to see the code on top of the chip ;) ). This particular chip is the one which provides the STAND-BY voltages 3.3V and 5V and the POWER-GOOD signal. If by some reason this chip is gone or fails to provide these stand-by voltages your MB will never power-up.

In my case, since one of the SWITCH selector MOSFETs was gone (you can read my first post) it was failing to provide stable power supply to the POWER MANAGEMENT chip and therefore the chip was failing to supply the board with STAND BY voltages and power good signal. And this was the reason why the MB was not powering up.

 

Bottom line:

1. Locate your 2 mosfets on your MB. They are labeled with PU4001 and PU4002 on your MB. Measure if they are OK.

2. Check the battery charger IC chip, power management IC chip and the MOSFETs attached to them.


How to check the IC chips - the first and simple way is to see if they get a stable power supply voltage. Both of these ICs need to get around 20V as power supply. If the power supply voltages for both chips are OK then check the output voltages of the PU4103 chip. Here you should get stable 3.3V and 5V if not replace the chip.

For the pinouts refer to the IC's datasheets. Just google and they should pop up.

 

The next step is the Embedded Controller EC but first let us see if your power block is OK.

 


Let me know if something from the above text is not clear.

 

Good luck!

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18 Posts

06-02-2011

Australia

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Re: E420 motherboard problems

2013-05-20, 21:16 PM
Hi,
Thanks for taking the time to look at this.
My problem is that the machine simply refuses to power on. The fan spins for 3 seconds and then turns off.
Called Lenovo and was told it was a faulty motherboard and because the laptopt was out of warranty (by 1 month!) the would charge me $450 to fix it (paid $600 for the unit when new).
Apparently the MOSFET issue is very common on many Lenovo laptops.
I will test the MOSFETs you mentined tonight and let you know the results.

Cheers.
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11 Posts

12-10-2012

Bulgaria

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Re: E420 motherboard problems

2013-05-21, 6:55 AM

BTW I have noticed that you have done something to the BIOS chip as well. It looks to me like you have desoldered and soldered it or something like this. Did you replace the BIOS chip?

 

FYI - The bios version and the EC (Embedded Controller) version should match. I have ordered newer version of the BIOS chip and soldered it on the MB but the EC was the older version and the MB was failing to power up. The fan was spinning couple of times and then turned off - no picture no sound just the fan.

 

Good luck!

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18 Posts

06-02-2011

Australia

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Re: E420 motherboard problems

2013-05-21, 8:20 AM

Hi Alpiweb,

 

This is turning to be a very entertaining exercise!

Ok, reason why you couldn't find MOSFETs PU4001 and PU4002 is because they are on the other side of the motehrboard! I found them and tested them and it looks like PU4001 may be dead, so I'm going to have a go at replacing both as you mentioned before.

 

I haven't done anything to this motherboard BUT the whole laptop was serviced once while on warranty so Lenovo mya have had a go at the BIOS chip for all I know but it definitely wasn't me.

 

I'll have a go at getting the mosfet replaced and see how that goes.

I may send soem moeny your way for all the help!

 

Cheers.

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11 Posts

12-10-2012

Bulgaria

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Re: E420 motherboard problems

2013-05-21, 8:59 AM

This good news NOT4US!

 

Please be aware of the damages that static electricity can cause on the MOSFETs. Just take some precautions and try to use plastic tools to lift and place the new mosfets (if you gonna do it by yourself ;) ).

 

And once you remove/desolder the old mosfets please measure/test them again (double check and confirm the fault) befere soldering the new replacements.

 

Please, keep me posted!

 

And GOOD LUCK!

 

p.s.

 

Do you mind sending me the picture of the top side of your MB with the location of the 2 mosfets, I would like to include the image on my 1st post so in this way it will help people who own Lenovo E420 as well.

Thank you!

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8095 Posts

11-19-2007

United States of America

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Re: E420 motherboard problems

2013-05-21, 17:10 PM

All,

 

The thread title of "motherboard problems" is pretty broad.  However, if your symptom is no power, while there could be multiple causes, some help may be available through support - please see the solution on this related thread on E520.


I'm going to mark this one as the solution because I want to ensure customers with no power symptoms contact support.  If you have other symptoms, or just want to continue a technical discussion regarding component level repairs outside of warranty on your own, then that is fine. 

 

 

EDIT 12-5-2013,  As noted on the last post in this thread and in the solution and last message on the E520 thread, the extended coverage ended 11-30-13.

 

EDIT - 12-15-13

 

There has been some confusion on this topic.  Coverage for this symptom had been extended through 11/30/2013 but that date has passed and so any further repairs must be done under the terms of the warranty - if your system has an extended warranty and it shows as in warranty, please contact service.  If your warranty has expired, repairs can be made on a fee basis through service.

 

Best regards,

 

Mark

 

 

0 person found this solution to be helpful.

This helped me too

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18 Posts

06-02-2011

Australia

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Re: E420 motherboard problems

2013-05-21, 22:00 PM
Mark_Lenovo thank you HEAPS for this.
If only I coudl have done this 10 months ago when my laptop died...
I just called support and explained my issue and pointed them to the different threads here in the Forums and even though my machine is out of warranty (expired in June 2012!) they are fixing **bleep** for me free of charge!!!
That is some pretty good customer service right there, pity it has taking Lenovo this long to finally get around the issue but hey, better late than never!
Again, thank you Mark and everyone else that has contributed to this, hopefully we can all get our computers fixed soon.
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6 Posts

05-24-2013

Australia

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Re: E420 motherboard problems

2013-05-24, 15:36 PM

Hi not4us

 

Howdy!

What did you do to get free repair for your crappy E420? I want to get mine fixed for free!

Thanks a lot!

 

Regards,

Jamie

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18 Posts

06-02-2011

Australia

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Re: E420 motherboard problems

2013-05-26, 2:02 AM
I just contacted support and told them about the problem with my E420 and that it was out of warranty but that I had been instructed by a Lenovo Representative in this forums to contact them as this should be fixed free of charge even if the laptop warranty was expired.
The nice girl I was speaking to then went to check with her manager and she came back telling me that it her manager had approved the repair free of charge and that they will be collecting the laptop from me soon.
On Thursday I received a return box and they will be picking it up on Monday to have it fixed at no cots to me, whohooo!
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