Lenovo Flex 2 14" LF14M MB 13281-1 Completely Dead

So I have problem again

Board No.:

LF14M MB
13281-1
448.00X01.0011

Initially the laptop came to me with faulty PU4402. Laptop was starting only for few seconds, then switched off & didn't charge the battery. I've replaced PU4402 & now it's 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? Thank you..

Is PU4402 new and properly soldered?

Lesio23 napisał(a):Is PU4402 new and properly soldered?

Yes...new & soldered properly...Strange thing is now I'm getting different readings on BQ24715:

PIN 1= 19V
PIN 2= 19V
PIN 3= 19V
PIN 4= 25V (like I've mentioned before)
PIN 5= 3.3V
PIN 6= 2.6V
PIN 7= 0V???
PIN 8= 0V???
PIN 9= 0V???
PIN 10= 0V
PIN 11= 6V
PIN 12= 6V
PIN 13= 6V
PIN 14= 0V
PIN 15= 0V
PIN 16= 6V
PIN 17= 12V
PIN 18= 6V
PIN 19= 6V
PIN 20= 19V

Also posting 3V/5V regulator voltages (it's TPS51275)

PIN 1= 1.2V
PIN 2= 0V
PIN 3= 3.3V
PIN 4= 0V
PIN 5= 0.9V
PIN 6= 2.6V
PIN 7= 0V
PIN 8= 0V
PIN 9= 4.7V
PIN 10= 0V
PIN 11= 0V
PIN 12= 6V
PIN 13= 5V
PIN 14= 0V
PIN 15= 0V
PIN 16= 0V
PIN 17= 4.8V
PIN 18= 0V
PIN 19= 0V
PIN 20= 0V

Measure the voltage and resistance of all coils relative to ground. A large part of the measurements with BQ is incorrect.
Measure the resistance to ground on pins 8, 10, 11, 15, 16 and 18 - TPS51275

PL4402=10MΩ - 6V (that's the battery line)
PL4501=1.9KΩ - 0V
PL4502=18KΩ - 0V
PL4801=1MΩ - 0V
PL4701=128Ω - 0V
PL4901=550Ω - 0V

I don't see shorts here, so...

All the VOLTAGE measurements I've done with battery & charger connected.

And resistance on TPS:

8=1KΩ
10=151KΩ
11=87KΩ
15=87KΩ
16=150KΩ
18=15KΩ

So, I've replaced BQ24715 & got different readings:

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 ???

The voltages on charger chip (BQ24715) seems ok now.

Measure the voltages to ground on pins 3, 6, 7, 9, 12, 13, 17, 20 of PU4501 with connected charger only (without battery connected).

matic napisał(a):The voltages on charger chip (BQ24715) seems ok now.

Measure the voltages to ground on pins 3, 6, 7, 9, 12, 13, 17, 20 of PU4501 with connected charger only (without battery connected).

3=3.3V
6=0V
7=0V
9=4.8V
12=9V
13=5V
17=0V
20=0V

Remeasure the voltage to ground on pin 17 of PU4501.
Does the battery charges?
Measure the voltage on the power button.

matic napisał(a):Remeasure the voltage to ground on pin 17 of PU4501.
Does the battery charges?
Measure the voltage on the power button.

Sorry, I was measuring wrong PIN. PIN 17 is 4.8V

Battery doesn't charge, no LED light

I have 3V on PWR button

Measure the voltages to ground on pins 6, 14, 17, 21, 64, 73, 102 of KBC chip.

Measure the voltages to ground on pins 93, 117 of KBC chip in the following cases:
a) Power button released.
b) Power button pressed.

matic napisał(a):Measure the voltages to ground on pins 6, 14, 17, 21, 64, 73, 102 of KBC chip.

Measure the voltages to ground on pins 93, 117 of KBC chip in the following cases:
a) Power button released.
b) Power button pressed.

KBC ( NPCE285GA) Voltages:

6=0V
14=0V
17=3V
21=0V
64=0V
73=0V
102=0V

PWR button released=>PWR button pressed

93=3V=>0V
117=0V=>0V

Measure the voltage to ground on pin 19 of KBC chip.

matic napisał(a):Measure the voltage to ground on pin 19 of KBC chip.

19=0V

The KBC chip standby power supply is missing.
Measure the resistance between pin 3 of PU4501 and pin 19 of KBC chip.

Was that board spilled?

matic napisał(a):The KBC chip standby power supply is missing.
Measure the resistance between pin 3 of PU4501 and pin 19 of KBC chip.

Was that board spilled?

PIN19 on KBC = 1KΩ
PIN3 on PU4501 = 35KΩ

No liquid damage on board. I think the problem is I have missing 3D3V_AUX_KBC voltage like I've mentioned above. According power sequence this voltage is pulled from 3D3V_AUX_S5, but I'm not sure though.

loser18 napisał(a):PIN19 on KBC = 1KΩ
PIN3 on PU4501 = 35KΩ

Not ground resistance, measure the resistance between that pins.

matic napisał(a):

loser18 napisał(a):PIN19 on KBC = 1KΩ
PIN3 on PU4501 = 35KΩ

Not ground resistance, measure the resistance between that pins.

Have 38KΩ

But is 3D3V_AUX_S5 connected straight to KBC? I thought there's some switch circuit betwen them.

But is 3D3V_AUX_S5 connected straight to KBC? I thought there's some switch circuit betwen them.

Usually not.

Use a thin wire and bridge the points "A" and "B" (Pictures below).

matic napisał(a):

But is 3D3V_AUX_S5 connected straight to KBC? I thought there's some switch circuit betwen them.

Usually not.

Use a thin wire and bridge the points "A" and "B" (Pictures below).

So you just want me to inject 3.3V to 3D3V_AUX_KBC_VCC or has this bridge any particular reason? Because I've got bench PSU...