Lenovo IP3 NM-D471 No power

[BlueRay]

This board has no power. I have 20v on PQ5400 pin 5678. ACDRV on Pin 4 = 0V. Tested change charging ic BQ24780s, no result. Try change PQ5400 and PQ5401 also same. try bypass PQ5400 and working find. i got the power and laptop turn on fine. No short circuit find.

28 VCC = 20v
24 REGN = 6v
6 ACDET = 2.6v
5 ACOK = 0v

For ACOK, can i get it directly from REGN pin on charging ic? On the schematic, PR5436 and PR5437 has no component attached. so if i put 2 100k resistor to get 3v acok. does its ok? or maybe i should check other component?

[MOD EDIT] Link to schematic -> https://www.badcaps.net/forum/troubl...15itl6-nm-d472

Reminder: rules and organization of this section -> https://www.badcaps.net/forum/troubl...f-this-section

[mcplslg123]

You cant generate ACOK forcibly. The IC is pulling ACOK low for some reason. Theoritically,even if ACOK is forced,ACDRV wont work as CMSRC is still missing. Resistance measurements for PQ5400/5401 between
Source-Gate
Source-Drain
Drain to Gate

[BlueRay]

You cant generate ACOK forcibly. The IC is pulling ACOK low for some reason. Theoritically,even if ACOK is forced,ACDRV wont work as CMSRC is still missing. Resistance measurements for PQ5400/5401 between
Source-Gate
Source-Drain
Drain to Gate

I measure them without desolder

PQ5400
Source to Gate : 3.9 ohm
Source to drain : 3.4 Mohm
Gate to drain : 5.5 Mohm

PQ5401
Source to Gate : 3.9 ohm
Source to drain : 4.0 Mohm
Gate to drain : 3.28 Mohm

[mon2]

Source to gate are in ohms or Mohms? If ohms, they are shorted. Be sure there is no power during resistance checks.

[BlueRay]

In Mohms. i dont think this two mosfet shorted. because i try remove PR5425. 20v can pass thru PQ5401. checked after PR5425. no short find.

[mon2]

ACOK is an open-drain output. For this reason, this line must have a pull-up resistor to park this line when the ACOK output is hi-z (high impedance / tristate). That is, if this line is NOT ok in case the power adapter is wimpy then this line will be pulled LOW by the charger IC. If the adapter is deemed to be OK, this line will float and therefore an external resistor must be present.

In tracing this ACIN netname, the resistor of interest appears to be @ RE89. Confirm it is present on your board and also confirm that you have a valid voltage for +3VL. Summary: ACOK is low because the power adapter is wimpy OR you are missing the +3VL rail to park this floating line (my guess is this condition - final answer).