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Old 04-23-2018, 10:37 PM   #21
JaroTech
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Default Re: very challenging issue! lenovo G50-80?

I'm curious, what resistance do you have to ground on pin 7 of PU905?
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Old 04-24-2018, 06:07 AM   #22
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Default Re: very challenging issue! lenovo G50-80?

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Maybe that's because the motherboard is revision 1.0 and the schemas are revision 0.4, they made some changes.
Good point .you are right it's a differennt rev!.. I think only injecting 3.3v via an external might show the defected component then.
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Old 04-24-2018, 06:33 AM   #23
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Default Re: very challenging issue! lenovo G50-80?

Yes, if you can inject 3.3V, it will help to find the bad component. But what about the value of the resistance on pin 7 of PU905 (just curious)?
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Old 04-24-2018, 06:37 AM   #24
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Default Re: very challenging issue! lenovo G50-80?

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I'm curious, what resistance do you have to ground on pin 7 of PU905?
There are couple of resistor to ground around pu904. But non of them is shorted. The short is not on the PU904 side. It is on the other side of the jumper PJ304. So the +3VLP signal has no short but the +3VL side has.
I tested every component connected to +3VL and they were all shorted except for the signal that enters the IO which was not shorted. Which confused me but I think this might be due to some schematics difference (my MB is rev 1.0 and schematics is rev 0.4) as per JaroTech suggested.

However, the only resistor to ground I found in the schematics was when +3VL meets PU202. Enter resistor PR225 which should be 100k but it 50k when connected to the circuit and 100k outside the circuit. Does that mean anything.
Though, when I renoved those two resistors the short was still present.
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Old 04-24-2018, 06:38 AM   #25
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Default Re: very challenging issue! lenovo G50-80?

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Originally Posted by JaroTech View Post
Yes, if you can inject 3.3V, it will help to find the bad component. But what about the value of the resistance on pin 7 of PU905 (just curious)?
I will check that too. And return back soon.
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Old 04-24-2018, 07:09 AM   #26
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Default Re: very challenging issue! lenovo G50-80?

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I will check that too. And return back soon.
there is no resistor to ground on pu905 pin7. only a capacitor PC1070. however, the pu904 pin7 have a resistor to ground 1M ohm.
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Old 04-24-2018, 07:19 AM   #27
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Default Re: very challenging issue! lenovo G50-80?

Sorry, what I meant was to measure the resistance to the ground.
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Old 04-24-2018, 07:35 AM   #28
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Default Re: very challenging issue! lenovo G50-80?

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i could not figure out the short place. But what made me confused is that there is no short to ground in the line from +VL to the IO chip. however, according to the schematics then it had to. but in reality all other +VL signals are shorted except for the Signal to the IO.
but i could not figure out the place of the resistant RE1 and RE3 to check if RE1 is the cause.

RE1 and RE3 are marked with '@' meaning they are no stuff. The power is taken from the +3VALW_R line just below.
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Old 04-24-2018, 07:38 AM   #29
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Default Re: very challenging issue! lenovo G50-80?

Aha! I see. Sorry I miss understanded it. The resistor to ground is 1.5M ohm.
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Old 04-24-2018, 07:38 AM   #30
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Default Re: very challenging issue! lenovo G50-80?

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Sorry, what I meant was to measure the resistance to the ground.
Aha! I see. Sorry I miss understanded it. The resistor to ground is 1.5M ohm.
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Old 04-24-2018, 07:43 AM   #31
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Default Re: very challenging issue! lenovo G50-80?

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RE1 and RE3 are marked with '@' meaning they are no stuff. The power is taken from the +3VALW_R line just below.
No stuff! But @ is under almost every jumper and they are present in the board. Sorry I am no very familiar with schematics, can you explain that bit please.

Thanks
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Old 04-24-2018, 08:30 PM   #32
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Default Re: very challenging issue! lenovo G50-80?

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Sorry, what I meant was to measure the resistance to the ground.
Finally I found the source of the short. It was UA1 ic. I used the method of injecting 3.3v to the board and waited for about an hour to feel that UA1 ic is slightly hotter than other components. I changed the ic but before I tested all the capacitors and resistors around it and they were all fine.
Now when I connect the power supply the power lead light up and there is no output. And when I hold the power botton the board doesn't turn off. I suspect the IO ic but not sure. And I don't have the io ic programmer.
But the 3.3v mission done all the thanks is to you. Your help is Really appreciated ... Thanks again
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Old 01-14-2019, 07:05 AM   #33
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Thumbs up Re: very challenging issue! lenovo G50-80?

Hello.

I own a Lenovo G50-80 with NM-A361 motherboard and have the same issue:
- When I try to turn on the laptop, the LED turns on for 1-5 seconds
- Then it turns off

No beeps, nothing appears on the screen, no nothing.

For two weeks, after several tries the laptop was finally booting up, but this past weekend it finally died.

After some research, I found this forum and some videos on YouTube.
I finally came across this one: https://www.youtube.com/watch?v=uIfBMkFB10E

So I did the same tests on my mosfets and it seems that very same is the one failing in my case.

I hope this info helps somebody else.
Regards.
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Old 01-16-2019, 01:58 PM   #34
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Default Re: very challenging issue! lenovo G50-80?

as first reflash bios.it is main issue on these boards
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Old 02-11-2019, 02:44 AM   #35
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Default Re: very challenging issue! lenovo G50-80?

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Originally Posted by ktmmotocross View Post
as first reflash bios.it is main issue on these boards
After changing the 4407 mosfet, now I see I've the correct voltages on the 2nd mosfet, but the laptop is still not booting.

As I don't have the needed hardware to reflash the bios, I've purchased one programmed replacement for the 25b64bsig chip in the ACLU3/ACLU4 NM-A361 motherboard, inside my Lenovo G50-80 (model name: 80E5).

I'll come back here to report when replaced.
Thanks for the suggestion.
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Old 02-11-2019, 04:57 AM   #36
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Default Re: very challenging issue! lenovo G50-80?

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After changing the 4407 mosfet, now I see I've the correct voltages on the 2nd mosfet, but the laptop is still not booting.

As I don't have the needed hardware to reflash the bios, I've purchased one programmed replacement for the 25b64bsig chip in the ACLU3/ACLU4 NM-A361 motherboard, inside my Lenovo G50-80 (model name: 80E5).

I'll come back here to report when replaced.
Thanks for the suggestion.

come on, bios flasher cost 2euros on aliexpress
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Old 02-12-2019, 02:49 AM   #37
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Default Re: very challenging issue! lenovo G50-80?

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come on, bios flasher cost 2euros on aliexpress
Ooops... such a big fail

My first search for the programmer showed +30€, and the programmed chip was just 16€, that's why I've purchased that way.

Anyway, as it's so cheap, I'll purchase the flasher for future research/repairs.
Thanks for the info.
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Old 02-12-2019, 10:34 AM   #38
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Default Re: very challenging issue! lenovo G50-80?

dont know if this lenovo have 3V or 1.8V bios ic, so u better buy 1.8V adapter with programmer for 1 or 2 euros
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Old 02-12-2019, 10:51 AM   #39
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Default Re: very challenging issue! lenovo G50-80?

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dont know if this lenovo have 3V or 1.8V bios ic, so u better buy 1.8V adapter with programmer for 1 or 2 euros
it is 3.3v bios. only lenovo g50-30 have 1.8v bios chip from g50 lenovo series.
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