HP Probook 4540S can't start

Model: HP Probook 4540S
Board id: Probook 4540S 11241-1 S-Series Riche

Laptop can't start. 19V is ok. But there is no volt on ADP_EN line. So 19V can't pass PU4001. When remove PQ4001, it' 3.3V on ADP_EN Line. But with PQ4001 there is no volt on ADP_EN. PQ4001 is ok. I replace PQ4001 with same mosfet. But nothing change. Need help.

Hello!

Measure the resistances to ground on pins 8, 16, 17 of chip PU4301.
If all resistances are high (in kΩ range or grater), measure the voltages to ground on pins 8, 13, 16, 17 of PU4301.

In schematic, PU4301 is a mosfet. Not an IC. If you mean PU4103,

1) Resistances are high
2)
Pin 8,13 - 3.3V
Pin 16 - 17.64V
Pin 17 - 5V

cygron wrote:In schematic, PU4301 is a mosfet. Not an IC. If you mean PU4103,

Yes, I mean PU4103. Sorry, my mistake.

- Measure the voltages to ground on pins 1, 3, 4, 5 of chips U3802, U3804.
- Measure the voltages to ground on pins 14, 15, 31, 39, 41, 42, 63, 64, 70, 74, 99, 100, 122 of KBC chip.
- Measure the voltages to ground on pins 4, 73 of KBC chip in the following cases:
a) Power button released.
b) Power button pressed.

U3802
Pin 1, 3 - 1.9V
Pin 4 - 3V
Pin 5 - 5V

U3804
Pin 1, 4 - 0V
Pin 3 - 1.9V
Pin 5 - 5V

KBC Chip
Pin 14 - 3.3V
Pin 15 - 1.8V
Pin 31 - 3.2V
Pin 39 - 1.4V
Pin 41 - 3V
Pin 64 - 3.3V
Pin 42, 63, 70, 74, 99, 100, 122 - 0V

Pin 4 - 0V ( power button press or release )
Pin 73 - 3.3V (release) / 0V (press)

Measure the voltages to ground on both pins of resistor R3811.

R3811 both side have 0V

Have you tested the machine with a genuine Hp power supply?
If so, measure the resistance to ground on pin 1 of diode D8201. If the resistance is high (in kΩ range or greater), check the continuity between central pin of the DC socket and pin 1 of resistor R3811. It's best to use a Hp or Dell service DC cable to check the continuity.

Diode D2801 pinout:

Adapter is the problem device. Change other HP original adapter and laptop is now running fine. Thanks for your helping and guide. Best regards.