Asus UX334F - Not Charging

[TheBlackPanther]

Re: Asus UX334F - Not Charging

Visual inspection also done again. All connections look fine.

[Ado02]

Re: Asus UX334F - Not Charging

After installing the replacement battery, the laptop charged very slowly, reaching only 20% before ceasing to charge altogether. Now it only runs off the battery, and when the charger is plugged in, nothing happens. The DC jack shows a voltage of 19v at the back.

Where should I go from here?

[mon2]

Re: Asus UX334F - Not Charging

Does the unit operate if using only the power adapter? (no battery)

[Ado02]

Re: Asus UX334F - Not Charging

No - just the battery. When the charger is plugged in, nothing happens.

[mon2]

Re: Asus UX334F - Not Charging

Ok. Then very likely a fault of the 2 * DCin mosfets.

Very carefully, you will need to measure the charger IC pins. If you are not comfortable with this, you can consider to measure the 2 x DCin mosfets.

Interested in the following review - meter in DC volts scale of 30v or higher.

Red probe to point to test; black meter probe to ground (shield is ok).

Measure the voltage to ground of:

Source (1-2-3) ; pick any pin from this cluster
Gate (4)
Drain (5-6-7-8) ; pick any pin from this cluster

Post each measurement. Repeat for the 2nd DCin mosfet.

Often, the gate voltage is NOT ~25v which is required to enable the 2 x DCin mosfets which in turn will power the board and charge your battery.

The root cause is often the 2nd DCin mosfet which gets damaged and must be replaced.

Post your measurements to proceed and then can check if the mosfets are ok or not.

[Ado02]

Re: Asus UX334F - Not Charging

Hi,

I measured the MOSFETs next to the DC jack.

M3056M - Drain 19v / 1-2-3 0 Gate 0
E180AJ - Drain 2.16v / 1-2-3 0 Gate

I attached image of the MOSFETs

[mon2]

Re: Asus UX334F - Not Charging

So gate voltage is not correct. It must be ~25v to enable.

Locate the ACDRV pin on the charger IC and there is a 4k resistor in series from this pin to the gates of the DCin mosfets.

Carefully flux and remove this 4k resistor. Do not lose the part.

Then power up again and check the voltage at the ACDRV pin pad where you removed to resistor.

Is the charger ACDRV pin to ground now ~25v ?

As per the sticky by @Piernov, often the 2nd DCin mosfet gets killed and causes the ACDRV voltage to tank.

[Ado02]

Re: Asus UX334F - Not Charging

Still 0v on ACDRV and ACOK

[mon2]

Re: Asus UX334F - Not Charging

See attached. Measure the voltage of REGN to ground.

[Ado02]

Re: Asus UX334F - Not Charging

1.19v

[mon2]

Re: Asus UX334F - Not Charging

That is not a good voltage. REGN should be ~6 volts.

Then ACDRV = adapter voltage + REGN = ~25 volts.

At this time, best to measure each pin voltage on the charger IC to ground.

Post the list of values and their respective pin numbers for a review.

We need to be sure that the charger IC is being powered, etc.

PS: Measure very carefully since the power is active to the logic board.

[Ado02]

Re: Asus UX334F - Not Charging

1 = 2.1v
2 = 2.1v
3 to 5 = 0v
6 = 2.6v
7 to 23 = 0v
24 = 1.2v
25 = 1.1v
26 to 27 = 0v
28 = 18.7v

[mon2]

Re: Asus UX334F - Not Charging

Remove all power. Meter in resistance mode.

Measure the resistance to ground of the REGN pin # 24. The voltage should be ~6 volts which it is not so there may be a shorted component on this rail which is causing this LDO rail to tank.

Next, locate the 2 x DCin mosfets that will be between the DCin power connector and the main power rail used to power the logic board.

The GATE pins of both of these DCin mosfets will be driven by the ACDRV pin of this charger IC but there will be a ~4k resistor in series of this pin.

Suspecting that you have a defective DCin mosfet which is causing chaos with the charger IC.

Remove all power -> meter in resistance mode -> measure the resistance across the DCin mosfets to check if they are defective.

Measure:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement. Repeat for both, the first and 2nd DCin mosfets.

[Ado02]

Re: Asus UX334F - Not Charging

M3056M

123-5678 = 1.3mΩ
567 - Gate = 1.3mΩ
123-Gate = 1.9mΩ

E180AJ

123-5678 = 1.8mΩ
567 - Gate = 0.73mΩ
123-Gate = 1.6mΩ

[mon2]

Re: Asus UX334F - Not Charging

These mosfet readings look ok. Based on the posted details, suggest to replace the charger IC. Aliexpress will have these. Recommend to also order spare mosfets that surround the charger IC as these parts are often the ones that fail.

Given that the charger IC is being powered ok (Vcc is fed from the raw adapter voltage), then REGN should be ~6 volts but it is not.

If you have not checked already, remove all power, meter in resistance mode.

Check the resistance to ground of REGN to confirm it is not shorted through the local filter capacitor.

Do the same for the ACDRV pin. Measure each directly at the charger IC body.

The DCin mosfets, etc. are very inexpensive and the same vendor of the charger IC can support the mosfet sourcing.

[Ado02]

Re: Asus UX334F - Not Charging

Problem was resolved with the replacement charging IC.

[mon2]

Re: Asus UX334F - Not Charging

Excellent. Good job and thanks for the closure details.