problem with a Dell Latitude 7400 notebook

[Markus1741]

Hello, maybe someone can help me.

The following problem with a Dell Latitude 7400 notebook.

ServiceTag: C5RBL13 Board number: LA-G871P Rev:1.0 (A00)

It doesn't start and when I read the voltage on the USB-C port, it fluctuates around 0.8 watts.

I measure it on the BIOS chip pin 8. It should be 3,3 volts.

There are 3,3 volts but I can only measure 0.2 volts. (+3.3V_SPI)

Is this the possibility that the PCH has a short circuit.

Schematic - https://www.badcaps.net/forum/troubl...56#post1587856

Thank you.

[mon2]

Review the voltage to ground of:

DCIN_CHG (pin 17 on PU700)
ADP (pin 16 on PU700)
ACOK (pin 24 on PU700)
PBAT_CHARGER_SMBDAT (pin 21 on PU700)
PBAT_CHARGER_SMBCLK (pin 22 on PU700)

[Markus1741]

Okay, here are the values you want, thank you.

DCIN_CHG (pin 17 on PU700) = 19,73 volt
ADP (pin 16 on PU700) = 19,60 volt
ACOK (pin 24 on PU700) = 0,003 volt
PBAT_CHARGER_SMBDAT (pin 21 on PU700) = 0,037 volt
PBAT_CHARGER_SMBCLK (pin 22 on PU700) = 0,038 volt

[mon2]

Remove all power. Meter in resistance mode (not diode mode).

Measure the resistance to ground of:

+13.5VB - this is the main power rail for the logic board. Checking for a shorted component with the resistance check.

+3.3V_ALW ; this rail is OFF as it can be observed with the ACOK / SMBDAT / SMBCLK lines being parked to a logic low - they need this rail to supply the pull-up voltage

+5V_ALW

The above rails will enable provided there is no short on each of the lines. Post each measurement.

[Markus1741]

Sorry, there is no short circuit anywhere. No mosfet, no capacitor.

[Markus1741]

Hello, I have +19.5V to PQ700 - AOE6936 then nothing, maybe 0.2V. I've already replaced the PQ700 Mosfet, no change.

[Markus1741]

Measure the resistance across the following DCin mosfet pins of PQ700:

D2/S1 = 53,1 k Ohm
D1 = 143 k Ohm
G2 = 10,7 M Ohm
G1+S1/D1 = 146 k Ohm
D1 = 53,1 k Ohm