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

[zaurus81]

I have the same database (paid) for schematics as you, search GA401QM page 92
I try to start the board with the bench power supply, without the diode

[zaurus81]

With sensing resistor in place and diode removed i've 4.3 volt unstable (up and down from 3.9v to 4.7v with multimiter) on main power line. So diode has nothing to do with it.

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance between pins # 1 and #2 on the charger IC. What is the resistance in ohms (with the current sense resistor onboard)? Measure directly on the charger IC contacts.

[zaurus81]

0.9 Ohm (resistance between red probe and black probe 0.4 Ohm )

[mon2]

On your board, do you see any resistors between pins #1 and #2 - other than the current sense resistor? What are the markings on the current sense resistor? Is this current sense resistor the original that was onboard?

The current sense resistor, to me, appears to be quite high @ 0.5 ohms = 500 milli-ohms (assuming there are no other resistors in this path).

[zaurus81]

resistor marking code is R005 and it is the original that was onboard. I don't think my multimeter is capable of measuring 5m Ohm.
I don't see any other resistances on the lines of pin 1 and 2 of the bq.
This mysterious voltage (4.3V) is present with and without the current sensing resistor.
Do you think it is a good idea to connect pins 1 and 2 with cables directly to the resistor?

[mon2]

No. You should have the SAME resistance if shorted or with the resistor. That is, your baseline short resistor is 0.4 ohms. But with resistor, you have 0.9 ohms so the current sense resistor is showing up as a 500mOhms (not 5mOhms). Suggest to hunt for a similar resistor to see if that makes a difference.

You should measure ~0.4 ohms WITH this current sense resistor installed.

[zaurus81]

ok I understand what you mean. Small clarification. If I measure the resistance between pin 1# and 2# of the BQ I get 0.9 ohm. If I measure the resistance across the sensing resistor I get 0.4 ohm. This is strange since I am measuring the resistance across the same 2 lines. Only 2 component can be involved: BQ chip and capacitor across acp and acn. there are also other 2 cap connected to ground, one for each line

[mon2]

Remove all power.

Measure the resistance from pin #1 on the charger ic to one side of the current sense resistor. What is the resistance? It should be 0R4 ohms.

Repeat with pin #2 on the charger ic to other side on the current sense resistor. Should be 0R4 ohms.

To keep it simple, flux and remove the current sense resistor. Then do the above tests.

Test the removed resistor. This measurement should also be 0R4 ohms across the contacts while the part is on your workbench.

[zaurus81]

With current sense resistor removed i have:

0.4 ohm from pin #1 on BQ to one side sense resistor (I have already subtracted the resistance of my probes from this value)

0.4 ohm from pin #2 to other side of current sense resistor (I have already subtracted the resistance of my probes from this value)

the removed resistor is ok because i read the resistance of my probe.

So there is a problem (400m Ohm - 500m Ohm) on these two rail

[mon2]

When you short your probes, what is the resistance?

what is the exact resistance of the current sense resistor?

The current sense resistor should the be same value as when you touch the meter probes together. If not, this resistor is defective and must be replaced.

[zaurus81]

shorted probes give me 0.3 ohm (yesterday it gave me 0.4 ohm, today i clean my probes)

current resistor give me a value of 0.3 ohm

[mon2]

With the current sense resistor off the board, measure the resistance to ground on each pin.

pin #1 to ground.
pin #2 to ground.

what is the resistance of each?

[zaurus81]

Pin #1 9Mohm
Pin #2 20Mohm

I found a video on yt with a similar problem......I dont know if i can post the link here......video is made by Sorin (search Asus rog G731G)
He found a problem on OVP voltage protection ciurcuit, which drive to ground the gates of ACFET and RBFET (ACDRV). My circuit is a little different and i dont have schematic....only boardview. Could I please use your knowledge to study the above circuit?

[mon2]

Flux and remove Q6008 off the logic board. Test again without this P-channel mosfet. Do not lose this part.

[zaurus81]

Flux and remove Q6008 off the logic board. Test again without this P-channel mosfet. Do not lose this part.

bordview says Q6008 is an n channel.

maybe it's Q6007

[mon2]

Good point. Flux and remove Q6004. I have a theory, just a theory that if we flux and remove all parts off the board, this mystery voltage will disappear. For now, let us start with Q6004.

[zaurus81]

I know that removing components for no reason makes no sense, and it's not my style even if I really like unsoldering. So don't consider what I told you in message 34#. In any case I removed the q6004 npn transistor and nothing changed.
Are the resistance values I wrote you in message 34# correct??
For me we can start the analysis from where we left off, from the sense resistor.

I noticed that if I connect a type c usb power supply equipped with a voltmeter to one of the ports, the voltmeter turns on and off as if it detected a short.
I did this because I saw that the laptop can also be powered by type c. See photo.
I'm just telling you this to inform you, let's continue with the sense resistor

[mon2]

Yes, resistance values look ok. No shorts.

Hunt for the resistor that is mated with the base pin of the removed transistor. Is the resistor value like your posted partial schematic?

If yes, carefully flux and remove this resistor since it is being driven by the ovp circuit and may be may be impacting the shutdown crowbar circuit. Do not lose these parts. Each is linked to the ovp circuit (over voltage protection).

[zaurus81]

Yes, resistance values look ok. No shorts.

Hunt for the resistor that is mated with the base pin of the removed transistor. Is the resistor value like your posted partial schematic?

If yes, carefully flux and remove this resistor since it is being driven by the ovp circuit and may be may be impacting the shutdown crowbar circuit. Do not lose these parts. Each is linked to the ovp circuit (over voltage protection).

Resistor (R6040) mated with the base pin of the removed transistor (Q6004) has a value of 1K (tested with multimeter), this value matches the one reported on boardview and on partial schematic.

with transistor and resistor out of the board i have 4.3 volt on main power line.