Asus TUF Gaming F16 (2024) FX607J no power no ACDRV

[zaurus81]

Hi all, I have a Asus TUF Gaming F16 (2024) FX607J motherboard with liquid damage. The oxide on the board was removed before giving it to me. This made it more difficult to repair. Also they did not give me the power supply.
When I connect the 20 volts with the bench power supply I get 4.3 volts on the main power line. If I remove the power sensing resistor I get 20 volts on one side (first 2 mosfets are ok) and 4.3 volts on the main power line (see photo). How is this possible?? I thought the 4.3 volts was coming from the battery mosfet so I unsoldered it and tested it. It is ok too. I also checked the 2 mosfets that charge the battery and they are ok.
The IC that manages the first two mosfets and the battery charging is the BQ24800. These are the values I get on the pins of the IC with the sensing resistor removed.

Pin 1 - ACN - 4,319
Pin 2 - ACP - 19.1V
Pin 3 - CMSRC - 19.02V
Pin 4 - ACDRV - 24.86V
Pin 5 - ACOK - 5.95V
Pin 6 - ACDET - 2.55 V
Pin 7 - IADP - 3.17V
Pin 8 - IDCHG - 0V
Pin 9 - PMON - 0.73V
Pin 10 - PROCHOT# - 0 V
Pin 11 - SDA - 3.3V
Pin 12 - SCL - 3.3V
Pin 13 - CMPIN - 0.26V
Pin 14 - CMPOUT - 6V
Pin 15 - BATPRES# - 0V
Pin 16 - TB_STAT# - 0V
Pin 17 - BATSRC - 0.21V
Pin 18 - BATDRV - 0.24V
Pin 19 - SRN - 0.21V
Pin 20 - SRP - 0.21V
Pin 21 - ILIM - 1.19V
Pin 22 - GROUND - 0V
Pin 23 - LODRV - 0V
Pin 24 - REGN - 6V
Pin 25 - BTST - 5.69V
Pin 26 - HIDRV - 0.21V
Pin 27 - PHASE - 0.21V
Pin 28 - VCC - 18.81V

When the sensing resistor is present I have completely different values on the IC and ACDRV from bq24800 is absent.
I also checked the integrity of the ACP and ACN lines that start from the ic and arrive at the sensing resistor. The lines are not interrupted (i read a topic in this forum ).
Attached you will find photos and bordview of the board, thanks in advance to anyone who will answer.

[mon2]

Suggest to flux and remove the bq24800 and confirm there are no issues under this device. Reflow or better yet, replace this part and test again.

[zaurus81]

Thx for reply mon2. Ok I'll start with a reflow. The area is not oxidized and the contacts are good. How do you explain the 4.3 volts if the resistance is disconnected? the bordview clearly says that the 20 volts once exceeded the 2 initial mosfets must stop if there is no resistor. There are no other connections. Do you think 4 volts come from bq??

[mon2]

Disconnect the battery (if it is connected). Do you still have this voltage? If yes, then suspecting the leakage is from the BQ charger IC.

[zaurus81]

the battery has always been disconnected. One thing I forgot to mention is that I have no current draw from the bench power source.

[mon2]

Flux and remove the 4k resistor that will be in series with the ACDRV pin. Do not lose this tiny resistor.

Power up. Now the DCin mosfets are supposed to be OFF. What do you measure now on the ACP and ACN pins?

[zaurus81]

See photo for results. 4.3V and 0.3V
thx for your patience

[mon2]

Remove the 2nd DCin mosfet off the board. After you do this, measure the voltage to ground on each pin on the remaining 1st DCin mosfet.

When the 2nd Dcin mosfet is removed, allow it to cool down on your work table. Then, meter in resistance mode.

Measure the removed mosfet as follows:

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. With the 2nd dc in mosfet removed, do you still see a voltage on ACP or ACN? If yes, for sure the charger IC is defective and must be replaced. Suspecting the power path for this leakage is through the Vcc pin on the BQ charger IC.

[zaurus81]

Voltage to ground of 1st DCin mosfet are:

Gate 25V (i have resoldered 4.2K resistor in series on ACDRV line)
Drain 20V
Source 20V

Here the values of 2nd Dcin mosfet out of the board:

source (1-2-3) & drain (5-6-7-8) ----> 0L (with inverted probes 3.6Mohm, i don't know why)
source (1-2-3) & gate (4) --------------> 0L
gate (4) & drain (5-6-7-8) --------------> 0L

I also checked the mosfet in diode mode. I read the voltage drop of the diode integrated in the mosfet from source to drain (red probe on the source and black on the drain, N-channel). Also when I apply the red probe to the gate and the black to the source I get conduction between drain and source (0.002). This indicates that it is working.

With the 2nd dc in mosfet removed, i see same values (see photo).
Looks like I need to buy a new bq24800.

[mon2]

Disconnect the battery (if it is connected). Connect the external power adapter. Measure the voltage to ground on each pin of the commonly used dual diode on the Vcc pin 28 of this IC. This is a dual common cathode diode with one leg feeding the power adapter voltage; other leg feeding the battery voltage to power this BQ charger IC.

Confirming if this dual diode is leaking and causing this mystery voltage to appear onto the ACN pin. Test all 3 pins on this dual diode.

[zaurus81]

In photo you read voltages values to grounds of each pin of this dual diode.
In diode mode i read 0.289 voltage drop for each diode (red probe to anode and black probe to cathode). Reverse it give me 0.L.

If you need i post boardview on appropiate section

[mon2]

This dual diode appears to be ok. Replace the charger IC and do update this thread.

[zaurus81]

Ok, thanks for your time. I just ordered the charger ic, it will arrive in 4 days. As soon as I mount it I will update the thread

[mcplslg123]

Some of the asus gaming boards wont work with bench PSU and there will be no 25V at ACDRV. When original adapter is used,ACDRV works fine at 25V. faced multiple times. So before experimenting,use a original charger first.

[zaurus81]

Some of the asus gaming boards wont work with bench PSU and there will be no 25V at ACDRV. When original adapter is used,ACDRV works fine at 25V. faced multiple times. So before experimenting,use a original charger first.

This is something I thought of right away. Unfortunately I don't have the original charger, which is a 20V 12A charger. My bench power supply gets to 5A. However when I disconnect the sensing resistor I get 25v on ACDRV.

[zaurus81]

Here I am. New bq just installed. Nothing changed. I still have 4.3 volts on the main power line with the sensor resistor removed from the board

[zaurus81]

20 volts coming from the power jack (PVADPTR line) goes to the diode D6001 passing through the resistor R6016 (13.7K). This is a switching diode (datasheet) and this is where the 4.3 volts are generated. By removing the diode I no longer have 4.3 volts in the sensing resistor. I tested the diode out of circuit and it seems ok. Unfortunately I don't know what function this diode performs and if it is doing its job. See boardview

[mon2]

Post a clear pic of D6001. Wish to confirm the smd markings to confirm against the diode datasheet.

Continue to trace each pin of the mystery rail. This would have been helpful earlier.

[zaurus81]

Smd Marking code is A7t. I found this diode in another asus schematic. see photos

[mon2]

That is a great find! Was hunting for the same but could not find it. Which schematic are your referencing with this partial screen grab? It can help us debug your case.

Leave this diode off the board. Without this part - is the board able to operate normally?

PS: The lack of using the originally beefy adapter is of concern. Purchase / borrow a suitable adapter. Maybe available through Amazon?