Asus UX334F - Not Charging

[Ado02]

Hi,

I am trying to fix a charging problem on an Asus UX334F.

When the charger is plugged in, the orange light comes on but starts to blink after 10 or so seconds. I replaced the battery, but this didn't resolve the problem.

On inspecting the charging IC BQ24780S (charger plugged in) - LODRV is not present (with or without the battery) - Phase 11.7v with battery and nothing without / ACOK 6v with or without the battery.

In the attached image, I circled the area that seems short to ground when the charge is plugged. However, as soon as you plug the charger out, the short go.

I would be grateful if you could provide me with guidance on where to look next and how to resolve this problem.

Thank you.

[mon2]

Re: Asus UX334F - Not Charging

Blinking Orange : The Notebook PC is running on battery mode and the battery power is less than 10%.

This should not be the outcome if the adapter is plugged in.

What is the voltage to ground on pin #4 (ACDRV) on the charger IC ?

If the adapter is plugged in, it should be ~25 volts.

[Ado02]

Re: Asus UX334F - Not Charging

This should not be the outcome if the adapter is plugged in.

What is the voltage to ground on pin #4 (ACDRV) on the charger IC ?

If the adapter is plugged in, it should be ~25 volts.

VVC - 19v
REGN- 6V
CMSRC - 19V
ACDRV - 0v
ACOK - 6v
ACDET - 2.48v

Area around the battery connector shorted when the charger or battery connected including the MOSFETs, coil and caps. But the short goes when no power is applied.

[mon2]

Re: Asus UX334F - Not Charging

Be sure that you are not measuring in resistance mode with power to the logic board.

With care, apply a bit of flux with low air pressure and remove the 4k resistor on pin #4 of the charger IC.

Do not lose this part.

Then power up again and measure again the voltage to ground of pin #4 on the charger IC.

What is the measurement?

[Ado02]

Re: Asus UX334F - Not Charging

I measured the 4k resistor, and it's not showing up as short. Do you still think it will need to be removed?

The mosfet (1st from the top on the picture next to the coil) - the gate has not voltage.

The other two mosfets do when the battery is connected.

[mon2]

Re: Asus UX334F - Not Charging

The charger IC is driving 2* DCin mosfets with the ACDRV pin. Common gate connection to the ACDRV pin.

If one the mosfets is leaking, the ACDRV voltage will be missing or be a lower voltage.

Suspecting that you have a defective mosfet.

The resistor has to be removed to confirm the ACDRV voltage at the charger IC.

[Ado02]

Re: Asus UX334F - Not Charging

The charger IC is driving 2* DCin mosfets with the ACDRV pin. Common gate connection to the ACDRV pin.

If one the mosfets is leaking, the ACDRV voltage will be missing or be a lower voltage.

Suspecting that you have a defective mosfet.

The resistor has to be removed to confirm the ACDRV voltage at the charger IC.

Thank you for your advice. I will remove the motherboard tomorrow and remove the resistor.

Which MOSFET would you start with? Also, can you recommend any checks I do before removing them?

[mon2]

Re: Asus UX334F - Not Charging

Start with removing the black vertical resistor that is under the 'T' marking of the charger IC.

That is the ACDRV pin resistor.

Keep the heat away from your LCD screen.

If the resistor is visible to you, you can remove it now. Be sure there is no power and the battery is disconnected.

[Ado02]

Re: Asus UX334F - Not Charging

Start with removing the black vertical resistor that is under the 'T' marking of the charger IC.

That is the ACDRV pin resistor.

Keep the heat away from your LCD screen.

If the resistor is visible to you, you can remove it now. Be sure there is no power and the battery is disconnected.

I got the ACDRV measurement wrong. The multimeter was set to 20v.

ACDRV: 24v
PHASE: 0v

Positive Battery Pins 8.4v on solid orange charging light. This drops to almost 0v when the light starts to flash. The same for the signal pin: 3.2v to 0.

What next?

[mon2]

Re: Asus UX334F - Not Charging

1) it is possible the battery is defective. Do you have access to another or is this a new battery?

2) it is possible that the current draw on the charging rail is too high so the rail is being shutdown.

3) the current draw will be deemed too high if the current sense circuit is not working properly.

Review the attached partial reference schematic.

Remove all power -> meter in lowest resistance scale.

Measure the resistance from the IC pin 1A to 1B - what is the reading ?

Measure the resistance from the IC pin 2A to 2B - what is the reading ?

The current sense path (above) must be present and similar to the attached schematic - engineers often clone the ref designs so Asus will be the same or very very similar. If one of these legs is broken, the charger IC will not gauge the current sense properly and shut down the charging process.

[Ado02]

Re: Asus UX334F - Not Charging

1) it is possible the battery is defective. Do you have access to another or is this a new battery?

2) it is possible that the current draw on the charging rail is too high so the rail is being shutdown.

3) the current draw will be deemed too high if the current sense circuit is not working properly.

Review the attached partial reference schematic.

Remove all power -> meter in lowest resistance scale.

Measure the resistance from the IC pin 1A to 1B - what is the reading ?

Measure the resistance from the IC pin 2A to 2B - what is the reading ?

The current sense path (above) must be present and similar to the attached schematic - engineers often clone the ref designs so Asus will be the same or very very similar. If one of these legs is broken, the charger IC will not gauge the current sense properly and shut down the charging process.

I am sorry, but I can't figure out the test point.

Can you point me in the right direction on the attached image?

Pin 20 is SRP - the CAP after the resistor is shorted while the caps next to it are fine.

[Ado02]

Re: Asus UX334F - Not Charging

Can you provide any further assistance on this?

[Ado02]

Re: Asus UX334F - Not Charging

Update: I ordered a replacement battery from Asus. I will update on the progress once the replacement battery has been replaced.

[TheBlackPanther]

Re: Asus UX334F - Not Charging

Update: I ordered a replacement battery from Asus. I will update on the progress once the replacement battery has been replaced.

Hello Ado02,

This is my first post to this forum. I have exactly the same issue with my sons UX334F and already tried 2 new batteries (no Asus originals). 8.4V drops to 0 when the orange led starts to blink, etc.

Were you able to fix the issue with you laptop?

[TheBlackPanther]

Re: Asus UX334F - Not Charging

1) it is possible the battery is defective. Do you have access to another or is this a new battery?

2) it is possible that the current draw on the charging rail is too high so the rail is being shutdown.

3) the current draw will be deemed too high if the current sense circuit is not working properly.

Review the attached partial reference schematic.

Remove all power -> meter in lowest resistance scale.

Measure the resistance from the IC pin 1A to 1B - what is the reading ?

Measure the resistance from the IC pin 2A to 2B - what is the reading ?

The current sense path (above) must be present and similar to the attached schematic - engineers often clone the ref designs so Asus will be the same or very very similar. If one of these legs is broken, the charger IC will not gauge the current sense properly and shut down the charging process.

Dear Mon2,

Thank you for the thorough explanation. With your drawing I have measured the resistances as you recommended. However I did not identify Rsr yet (drawn between 1B and 2B). What I measured:

Between 1A - 1B: 10,2 Ohms
Between 2A - 2B: 10,2 Ohms
Between 1B - 2B: 0,2 Ohms

Could I have a shorted C11? It 's actually the same situation as Ado02 discovered on his motherboard.
Or do you have another suggestion?

I attached a picture of the situation on the MB.

Thanks again!

[mon2]

Re: Asus UX334F - Not Charging

The readings look good.

You should also check the complete current loop resistance with a meter probe on 1A and other probe on 2A. This will validate the loop is complete. Should be @~20 ohms.

If you remove the adapter and mate the pre-charged battery, does the laptop boot like a normal unit?

What is the history of this laptop? Any liquid damage? Or just failed to work one day?

[TheBlackPanther]

Re: Asus UX334F - Not Charging

Happy with the quick support!

1A-2A measures 20,6 Ohms (sum of the 3 measurements in the loop).

The laptop indeed boots like a normal unit with the pre-charged battery.

History of the laptop is that the original battery did not charge anymore and it had grown so big that the keyboard was lifted up. My 15y old son didn't tell me, only after the teachers at school said he needed to have his laptop fixed because it should run on batteries. When I saw the situation I immediately removed the old battery and ordered a new one from Amazon.

No other accidents with the laptop, all seems to work fine except charging which stops after a few seconds.

[TheBlackPanther]

Re: Asus UX334F - Not Charging

Now I see that this Rsr in the schema you posted measures 10 milli-Ohm, which explains why C11 looks shorted.

I haven't found it yet on the board, but it will probably be there.

[mon2]

Re: Asus UX334F - Not Charging

1A-2A measures 20,6 Ohms (sum of the 3 measurements in the loop).

This is a good reading and confirms the current loop is complete.

LOL - my son (same age) also has an Asus that needs life support but he will not allow me access to it. He constantly uses it for his schoolwork and game consulting business he has started.

Have seen numerous bloated battery faults but mostly with macbooks.

The event warps the trackpad and/or interconnect cables get damaged.

Can you take a close visual inspection of the logic board / connectors to be sure that some part did not get moved or damaged during this battery expansion?

After the above, with great care, it will be best to review the voltage to ground readings (meter in DC volts; 30v or higher is ok) of each pin on the charger IC.

It is the charger IC that will detect whether the main power adapter and/or battery are connected. Respectively will shut off one power path for the other using the external mosfets (solid state switches / relays) to allow for the adapter or battery to power the logic board.

If the pre-charged battery is able to function and power the board, that is a good start.

What I do not know, yet, is if Asus has a 'whitelist' of compatible battery packs which it stores inside their bios. That is, they may demand that you have only an official battery from them before they will charge it. It is a far fetched thought but vendors have done this in the past.

If your battery vendor or internet searches confirm that it is possible to replace the battery, then ignore this comment.

The battery is a smart device and contains its own BMS (battery management system) microcontroller and firmware.

On the battery pack are 2 lines = SMBUS SCL & SDA pins which are used to communicate with the main logic board to extract the vital stats of the battery pack. The communication is really I2C but I2C is a trademark by Philips Semiconductor so to avoid the need to pay royalties to Philips, the industry called it SMBUS.

Ironically, Philips is one of our top customers for our products - 20+ year supplier to their medical group.

We need to be sure that the SMBUS lines are not damaged. With care, you can measure the voltage to ground of these 2 lines. Just measure each pin to ground on the battery pack and we will figure out which ones are the SMBUS lines. A good reading should be ~3 volts on the SMBUS lines.

If either of the SMBUS lines are not this voltage, then the communication to the logic board may be failing and then the charger IC will believe the battery pack is absent so no point to enable the charging mosfets.

[TheBlackPanther]

Re: Asus UX334F - Not Charging

Game consulting business..., what a professions there are these days. I googled for it and definely need to tell my son about it lol.

I will measure the voltages on the charger IC, but I need better probes for that to be sure not to damage anything. Ordered those.

About the battery I can say that the SMBUS lines both measure 3.21 volts, also when the charging light starts to blink after a while.

I tested once more if the laptop starts without power connected and with battery. It does but Windows reports there is no battery. That also doesn't come when you delete the battery from device management. So the battery is not seen, although it's power can be used.

Thanks again, will measure as soon as I received better probes.