Lenovo Flex 2 14" LF14M MB Please help me to identify component

[loser18]

Hi there...

Board No.:

LF14M MB
13281-1
448.00X01.0011

I've got Lenovo Flex 2 14" which doesn't charge battery. Sometimes it starts only for about 10 seconds & then cuts off. If I got lucky & manage to boot to windows, it shows battery fully charged with crossed battery icon. When I disconnect the charger it will cut off immediatelly. I can hear some buzzing noise from component PU4402 which says 49AG3 L393 on it (please refer to the pic). Any idea what component is it as I can't find schematic for this board? Thanks in advance.

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Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

Seem it's LM393DR-GP with TSSOP8 package, not sure 100%. (modern packages, not like old LM393 SOP8)

If we read Wistron Storm2 schematic, there is IC LM393 on block charger.

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

Seem it's LM393DR-GP with TSSOP8 package, not sure 100%. (modern packages, not like old LM393 SOP8)

If we read Wistron Storm2 schematic, there is IC LM393 on block charger.

You're right...Just found out it's TI LM393 voltage comparator in TSSOP8 package...

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

So I've replaced PU4402 & now the board is dead.

PU4402 Voltages:

PIN 1= 0V
PIN 2= 1.9V
PIN 3= 2.9V
PIN 4= 0V
PIN 5= 0V
PIN 6= 0.9V
PIN 7= 0V
PIN 8= 0V

BQ24715 Voltages:

PIN 1= 19V
PIN 2= 19V
PIN 3= 19V
PIN 4= 19V (pretty sure this should be 26V)
PIN 5= 0V
PIN 6= 2.6V
PIN 7= 0V
PIN 8= 0V
PIN 9= 0V
PIN 10= 0V
PIN 11= 0V
PIN 12= 6.6V
PIN 13= 6.6V
PIN 14= 0V
PIN 15= 0V
PIN 16= 0V
PIN 17= 0V
PIN 18= 6.6V
PIN 19= 6.6V
PIN 20= 19V

Any ideas?

[on/off]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

So I've replaced PU4402 & now the board is dead.

Any ideas?

Maybe The IC LM393 configuration like on Wistron Round rock.
Good idea is to confirm that PU4402 is LM393 family, check pin 8 connect to 5V_S5, pin 4 is GND and also other each pins (this job need more effort because IC charger and few small components at other side of board).

There are 5 schematics of wistron that use LM393 could found on pages 40-44:


Colossus

Latitude3000

EA40_HW

Hadley15

Storm 2


Round rock


HD image link
Credit to Rimas.

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

OK...So, I have replaced BQ24715 because those readings were wrong. New voltages:

1=20V
2=20V
3=20V
4=25V
5=3V
6=2.6V
7=0V
8=0V
9=0V
10=1.4
11=9V
12=9V
13=9V
14=0V
15=0V
16=6V
17=13V
18=9V
19=9V
20=19V

All measurement done with battery connected.

I think the problem is motherboard doesn't enter into S5 state as I've missing 3D3V_AUX_KBC voltages on all pins (19,46,76,88,115) of KBC (it's a NUVOTON NPCE285). There's no short on them. As far as I understand the 3D3V_AUX_KBC voltage is pulled down by Q2402 FET which should be activated by PSL_OUT# signal. This signal must be low, however it reads 3.3V ???

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Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

What about AC_IN# signal?

Purpose to know pinout NPCE285P
Link:

• https://www.badcaps.net/forum/showpo...02&postcount=4

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

PSL_IN1# = AC_IN# on PIN74 is low (0V)

AC_IN_KBC# is also low

[SMDFlea]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

What about AC_IN# signal?

Purpose to know pinout NPCE285P
Link:

• https://www.badcaps.net/forum/showpo...02&postcount=4

The suamain link goes to a 404 error page.

This link is working: http://suamainlaptop.com/uploads/files/schematics/

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

Does anyone know what signals must be present on NPCE285 before it sends PSL_OUT# ?

[SMDFlea]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

Check page 96 of the cedar schematic posted by on/off , 3D3V_AUX_KBC "Red Words: Controlled by EC GPIO"

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Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

I think the problem is motherboard doesn't enter into S5 state as I've missing 3D3V_AUX_KBC voltages on all pins (19,46,76,88,115) of KBC (it's a NUVOTON NPCE285). There's no short on them. As far as I understand the 3D3V_AUX_KBC voltage is pulled down by Q2402 FET which should be activated by PSL_OUT# signal. This signal must be low, however it reads 3.3V ???

I don't see Q2402 in my HD image. LF14M_448.00X01.0011_Rev13281-1_photo-mb

only see Q2403. on redwood schematic seem q2402 not installed.

Wistron Redwood Wistron Redwood also use NPCE285P (in fact your board use NPCE285G) and same IC charger BQ24715.
The suffix G that could be mean programmable, but not sure.
on Redwood Suffix P, but there is ec eeprom MXIC25L100 (programmable external meaning). Redwood HD image :
http://ascnb1.ru/forma1/viewtopic.php?p=680558#p680558

I'm confuse right now about signal AC_IN#, active low or active high.

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

I don't see Q2402 in my HD image. LF14M_448.00X01.0011_Rev13281-1_photo-mb

only see Q2403. on redwood schematic seem q2402 not installed.

Wistron Redwood Wistron Redwood also use NPCE285P (in fact your board use NPCE285G) and same IC charger BQ24715.
The suffix G that could be mean programmable, but not sure.
on Redwood Suffix P, but there is ec eeprom MXIC25L100 (programmable external meaning). Redwood HD image :
http://ascnb1.ru/forma1/viewtopic.php?p=680558#p680558

I'm confuse right now about signal AC_IN#, active low or active high.

Well I'm using Wistron Cedar as a reference. I Couldn't also find Q2402 on mobo ( it's marked as Q2404 on Redwood schematic), but thought it will be similar architecture. Even most of the components marking numbers are right with my one. It's really hard without schematic.

About the AC_IN# signal, it should be active low? Why are you confused about that?

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Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

• Cedar use BQ24737, usually need signal low for acok or acin or pwr chg acok as signal reportting to KBC that there is an ac adapter connected and has been verified ok (by some circuit internal BQ737). Even though that pin was pulled up to 3D3V_AUX_S5 but via 100k i think not generated be 3V, because when AC_IN# high, then result PWR_CHG_ACOK will off. While PWR_CHG_ACOK should be high to make PQ4402 pin 5 off but pin 2 on to generate PU4402, right?

• Redwood use BQ715 need Acok high. already prove by PQ4407 working ACN and ACP got 20V.
  When ACAV_IN (PWR_CHG_ACOK) high, Does it generated AC_IN#? or make 3D3V_AUX_S5 flow to gnd. Why i'm confuse because resistor 100K, if only via 10K i believe will flow to gnd and result low signal.
  if AC_IN# going high it hasn't effect to PQ4407, right?

hope easy to understanding. (my english very poor)

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

I see now...

I should have been clearer. I'm using cedar for KBC circuit only. For charging and 3V & 5V circuit I'm using wistron Hadley 14 schematic.I'm pretty sure that BQ and TPS voltages are OK.

[on/off]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

I see now...

I should have been clearer. I'm using cedar for KBC circuit only. For charging and 3V & 5V circuit I'm using wistron Hadley 14 schematic.I'm pretty sure that BQ and TPS voltages are OK.

I'm pretty sure too about that when you ask there is no supply for KBC.

ac_in# signal more wisely wait for other opinion else. there is a risk since no schematic.

while waiting good idea is to trace few signals power of sequence on page 99 (redwood) like RTC_AUX_S5 and next. because there is connect to KBC too.

[loser18]

Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

As I can see Redwood got different power sequence... Even KBC is connected different way...maybe I was looking on completely wrong schematic...now I'm confused,LOL...

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Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

I didn't understand what him talk, but there is something to think a about.

http://*******/viewtopic.php?f=58&t=83143

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Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

As I can see Redwood got different power sequence... Even KBC is connected different way...maybe I was looking on completely wrong schematic...now I'm confused,LOL...

Yes, Hard but not impossible, need your effort to trace many link/net on real board, maybe re-build schematic for match with LF14M (block by block).

At least we found more link resource at post #9

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Re: Lenovo Flex 2 14" LF14M MB Please help me to identify component

Also I'm notice on pin 76 KBC that is connecting to 3D3V_AUX_S5...