Dell Latitude 7410 no charge

[mon2]

S4 = P-channel mosfet. The gate voltage must be LOWER than the voltage being passed between source / drain pins to enable.

Remove all power. Meter in resistance mode.

Measure the resistance across this mosfet:

source / drain
source / gate
gate / drain

Post each measurement in ohms. Repeat for the S5 mosfet that follows.

[mon2]

Locate the following leg of the circuit.

Confirm this LDO @ PU2 is receiving a voltage from the power adapter. Confirm there is a voltage at the output of this same LDO @ +3.3V_VDD.

[Andreasbest]

Red Black
S4 P800
Source Gate 350Kohm
Source Drain 50Mohm
Drain Gate 50Mohm

S5 P801
Drain Gate 50Mohm
Source Drain 50Mohm
Source Gate 20Mohm


Black Red
S4 P800
Source Gate 20Mohm
Source Drain 20.75Mohm
Drain Gate 0.8Mohm

S5 P801
Gate Drain 0.8Mohm
Source Drain 1,5Mohm
Source Gate 25Kohm

Still looking for PR13

[Andreasbest]

Measured both combinations. Still looking for PR13

[mon2]

Pr13 will be a pcb trace. Just locate the ldo and test if there is a 3v3 output.

[Andreasbest]

Pr13 will be a pcb trace. Just locate the ldo and test if there is a 3v3 output.

What is the ldo ?

[Andreasbest]

Got it, you mean LDO, ok found it.
PU2:
Vin 4.7V
Vout 3.3v

[mon2]

Good. Go back to PQ800. Review the N-channel mosfet that is driving the gate. What is the voltage on the GATE pin of PQ807A?

There should be ~3v3 on the gate pin of PQ807A and this should turn ON PQ807A to create a voltage divider. This voltage divider will lower the gate voltage on PQ800 to enable it.

[Andreasbest]

Good. Go back to PQ800. Review the N-channel mosfet that is driving the gate. What is the voltage on the GATE pin of PQ807A?

There should be ~3v3 on the gate pin of PQ807A and this should turn ON PQ807A to create a voltage divider. This voltage divider will lower the gate voltage on PQ800 to enable it.

PQ807 has indeed 3.3v at Gate.
There is only one PQ807, what is this with the A and B?

[mon2]

The A and B means that this single package has 2 such mosfets inside.

Remove all power. Meter in resistance mode. Measure the resistance across pr811. Be careful because the part is a very small 0201 size. Is this resistance close to the schematic value?