Lenovo Legion 5 Pro 16ACH6H Water Damage

[Andreasbest]

Test the resistance across the 2nd dcin mosfet.

source / drain
source / gate
gate / drain

often 2nd dcin mosfet is defective and takes down the 1st dcin mosfet since they share the gate pins.

no power to the board during these tests.

S - D 7ΜΩ
S - G 7.19ΜΩ
G - D 12ΜΩ
With mosfet soldered on board.

[khaahk]

I was wrong about the work from battery, from the datasheet we read :

7.3.1.1
Battery Only
When VCC voltage is above UVLO, bq24780S powers up to turn on BATFET.

This is the PQ5403 on schematic, it connects the battery voltage to B+.
So this mainboard does not work without the charger ic.

I don't know no checks that can be done, it is ic-s internal fault. If mainboard has no further problems then it probably should work from battery.

[Andreasbest]

So i must order a new PU5401 to replace it and test it again, correct?

[khaahk]

So i must order a new PU5401 to replace it and test it again, correct?

Yes

[Andreasbest]

Ok, ordered 5 pieces. When they come i'mm come back with results

[funnypenguin]

Sorry to jump in on this one. I'm working on the same laptop that seems to be going through the same thing, no signs of life. Here's what I have so far. If anyone has any ideas or input I would be super greatful! I'm thinking maybe get a new 24780s?

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Resistances

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DC in MOSFETS

PQ5401, gate source drain no shorts

PQ5402 gate source drain no shorts

Main Power Rail to Ground 3 Mega Ohms


Current sensing lines

AC input current sensing amp inputs .7 ohm

Batt Current sensing amp 20 ohms

ACOK (pin 5) to ground .47 MegaOhms


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Voltages

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Main Power Rail Check

@ PR5401 Fluctuating 3.1-3.3v, not fully shorted.

Charger IC voltages


REGN (pin 24) 6.04v

VCC (pin 28) 19.7v

ACDET (pin 6) 2.62v

- TI manual says greater than 2.4v should be ok?

CMSRC (pin 3) .03-.35v

- Should be close to AC? something wrong?



ACDRV (pin 4) .02-.35v fluctuating with CMSRC and Main Power Rail.


ACOK (pin 5) 0v