DELL P40G (LA-9591P REV 1.0) no power

[madjid911]

Hello, I have a laptop DELL P40G (LA-9591P REV 1.0) that does not work, when I press the power button, the start LED sometimes lights up then goes out immediately.

I checked everything on the motherboard, no short, even the processor has good resistance, no liquid damage.

So I started to check the S5 voltages, I'm missing it +3.3V_M and +1.05V_M.

PU300 and U45 are well powered with +5V_ALW but PU300 does not give +1.05V_M (no EN_+V1.05SP neither), and U45 does not give +3.3V_M, there are no shorts around.

schematic and bordview : https://www.badcaps.net/forum/docume...ew#post3479536

Can you help me understand and find where the problem comes from please, I am not an expert

[madjid911]

SIO_SLP_A# : 0V, the processor is dead?

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of the VCORE power rail used to power the CPU. Share the measurement in ohms.

[madjid911]

Remove all power. Meter in resistance mode. Measure the resistance to ground of the VCORE power rail used to power the CPU. Share the measurement in ohms.

+VCC_CORE : 123 ohms

[mon2]

CPU is not shorted with such a high resistance.

Remove all power. Meter in resistance mode. Measure the resistance to ground of +3.3V_M. What is the resistance in ohms? U45 loadswitch may be defective.

[madjid911]

CPU is not shorted with such a high resistance.

Remove all power. Meter in resistance mode. Measure the resistance to ground of +3.3V_M. What is the resistance in ohms? U45 loadswitch may be defective.

yes I was also surprised to have a processor with such high resistance, it's the first time I've seen that

+3.3V_M : 0,488 MOHMS

[mon2]

Check the voltage to ground of pins 5, 6, 7 on U45.

[madjid911]

Check the voltage to ground of pins 5, 6, 7 on U45.

PIN 5 : 100KOHMS
PIN 6-7: 3,2KOMHS

[madjid911]

I will order U45

[mon2]

You have shared the resistance for the above pins.

Check the voltage on these pins (with the power or battery attached) to confirm the voltage is appearing at the input of the load switch AND the load switch is being enabled. Under this condition, the output voltage must be available unless the switch is defective. The output is not shorted so no reason for the voltage to be absent.

[madjid911]

You have shared the resistance for the above pins.

Check the voltage on these pins (with the power or battery attached) to confirm the voltage is appearing at the input of the load switch AND the load switch is being enabled. Under this condition, the output voltage must be available unless the switch is defective. The output is not shorted so no reason for the voltage to be absent.

Yes sorry, pin 6-7: 3V3. pin 5: 0V => same with the battery connected