Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

[Ado02]

Hello,

I am currently working on the Lenovo ThinkPad E14 Gen 2 with a GE4B0 motherboard.

Issue: The laptop runs on battery power, but it fails to recognize the charger. The LED1 indicator does not illuminate in white or orange when the charger is connected.

My investigation:

1. LB4709 and LB4708 both register 20V.

2. UE1:
Pin 34 ACIN_LED measures 0V at R31.
Pin 11 VCC_LPC_ESPI registers 0.27V.

3. +3VL_EC at R42532 and various other locations, following the schematics, measures 1.7V.

Charging IC: BQ25710

Measurements without battery connected only charger.

The Boardview and Schematics are attached. But from very similar boards.

MOD Edit - Link to Schematic https://www.badcaps.net/forum/showth...hlight=NM-D011
Reminder: rules and organization of this section https://www.badcaps.net/forum/showthread.php?t=117483
.

[Techtiger]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

What voltage do you have PU3 pin 15 ? PJ3/PJ4 ?

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

0v at RE135 (no component attached to these pads). I also did a check on Pin 15, but due to spacing I couldn't be sure - 0v

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

I just tested the same things on a working motherboard. On this one, it turns on when the charger is plugged in, but the power/charger LED doesn't light up. So, I assume the LED doesn't work when the charger is connected. Can someone confirm this?

Here are the results of my tests:

LB4709 and LB4708 both show 20V.

UE1:

Pin 34 (ACIN_LED) reads 0V at R31.
Pin 11 (VCC_LPC_ESPI) is at 1.8V.
Pin 15 is at 3.35V.

+3VL_EC at R42532 and various other spots, as per the schematics, measures 3.3V.

[Techtiger]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

0v at RE135 (no component attached to these pads). I also did a check on Pin 15, but due to spacing I couldn't be sure - 0v

didn't ask you to test RE135 signal. This is an input signal for the last stage of the power sequence. PJ3 is a test pad to check if your +3VALW is working or not, and PJ4 is a test pad to check if your +5VALW is working or not

[Techtiger]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

if PU3 TPS5139RJER is not producing LDO voltage on pin 15 (0V), then test the supply for the IC on any of pins 2, 3, 4, or 5

[Techtiger]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

What voltage do you get on PL4, PQ4, any pin 2, 3, 4, or 10? let us know

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

didn't ask you to test RE135 signal. This is an input signal for the last stage of the power sequence. PJ3 is a test pad to check if your +3VALW is working or not, and PJ4 is a test pad to check if your +5VALW is working or not

Faulty Motherboard PJ3 1.8V and PJ4 0v

On Working Motherboard: PJ3 3.36v and PJ4 5v

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

if PU3 TPS5139RJER is not producing LDO voltage on pin 15 (0V), then test the supply for the IC on any of pins 2, 3, 4, or 5

Faulty Motherboard:

1 - 1.58v
2 to 5 - 1.5v

Working Motherboard:

1 - 8v
2 to 5 - 9.24v

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

What voltage do you get on PL4, PQ4, any pin 2, 3, 4, or 10? let us know

Faulty Motherboard

PQ4 2 to 4 - 1.50v
PL4 - 0v


Working Motherboard:

PQ4 2 to 4 - 9.24v
PL4 - 9.28v

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

I think the VINT20_IN is missing.

F6101 1.5V is going up and down a little. If I am correct this should be 20V

[mon2]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

Check the voltage to ground on each side of the fuse F6101. Is it stable on one side?

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

Both sides go from 1.4v to 2.5v

[mon2]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

It is too low. Remove all power. Meter in resistance mode.

Measure the resistance to ground on each side of this fuse. Post each measurement.

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

I am unsure if I am doing something wrong, but the values consistently move on the faulty and working motherboard. But they always seem to be in the 1.200 Milliohms region but never stop moving.

[Techtiger]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

Follow simple basics:
01.Check resistance between
Source-Gate
Source-Drain
Gate-Drain
of both N-fets PB5/6

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

QB6

1-2-3 & 5-6-7-8 / 3.67 Mohms
1-2-4 & 4 / 4.00 Mohms
4 & 5-6-7-8 / At this point I noticed that the MOSFET started to lift away from the motherboard. So, I can only think it's shorted, and the solder has given way.

It's an E120GN Mosfet - I have a few other Lenovo motherboards around like 17812-1 - but I can't seem to find the same one. Any suggestions?

[Ado02]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

Solved:

Replaced QB6 AON7466 - found the same mosfet on another Lenovo motherboard and the charging is restored.

Thank you for your help...

[trufoldino157]

Re: Lenovo ThinkPad E14 Gen 2 / GE4B0 / Not Charging

Solved:

Replaced QB6 AON7466 - found the same mosfet on another Lenovo motherboard and the charging is restored.

Thank you for your help...

Thank you very much for your help, everything worked out. Respect.
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