Asus Zenbook 15 UX563FD 20v on first Mosfet D no power not loading

[dbuergi]

So i got my replacement board and everything is working besides the screen (track) pad.. I tried all trouble shooting with drivers and BIOS but nothing helped. Voltages are present and the screen x software wants to calibrate it but stops with an error.
Any ideas?

[dbuergi]

I removed several coils and mosfets but my voltage injection only showed GPU and GPU drawing 1v and 0,4a.
Since i already wrote the board off i removed the CPU and the coils went back to normal values but the short at the GPU stayed.
Never had a board where CPU and GPU died. So Case closed and i will try to get a replacement.

[mon2]

Reverse the meter leads and measure again from ACN to the cpu coils. Such a low resistance usually means that the high side mosfet on the cpu power rail is defective and this will result in nuking the cpu from the high adapter voltage leaking directly onto the cpu.

[dbuergi]

What is the resistance to ground of ACN? This is the main power rail.

Then test the resistance from ACN to the cpu rail coils.

What is the resistance?

ACN to GND 4,3 Ohms and ACN to CPU coils 6,8 Ohms.

[mon2]

What is the resistance to ground of ACN? This is the main power rail.

Then test the resistance from ACN to the cpu rail coils.

What is the resistance?

[dbuergi]

This board is giving me serious headache and i put it to the side for the next weeks.
Here are some more observations i made.

Mosfet 2 removed i get 20v through mosfet 1 and also gate shows 25,9v.
Voltage injection on source of mosfet 2 with 1v and 2a shows CPU heating up in the middle around 30C. On other coils i'm able to heat up GPU in the same way. No extraordinary heatspots. This is not the behaviour of dead CPUs or GPUs i saw before but i'm no pro.
All coils on sys_rail show 3 ohm. I removed nearly all mosfets on the board to test them in diode mode and all are fine.
With the JB2 diode removed i get my 2,7v on pin 6 of the BQ chip but it looks like a part which connects the battery rail to the rest of the board. ACN and ACP always show 0v and 8 ohm. BQ chip was replaced with a working one from another board and also a sare part from Digikey. So it is definitly not the problem.

Does it make sense to look any futher or is this board dead?

[dbuergi]

I have several coils around GPU and CPU showing 3-8 Ohm. I lifted the CPU coil and injected 1v with 1a on the 3 Ohm pad. Got directly 1V and 1A drawn but CPU went to 25-30C in the center.
So this is no short or am i wrong?

[mon2]

ACN 8Ohm
ACP 8Ohm

If these are resistance values to ground then the main power rail is shorted. Test the resistance to ground of each and every inductor on the board. Confirm if you see a similar measurement near the CPU.

[dbuergi]

Yes. What is the resistance to ground of ACN? ACP? This is the main power rail. Testing if it is shorted.

Also the ACDRV voltage should be ~25v to enable so the dcin mosfets are also suspects. If the main power rail is not shorted then the dcin mosfets are to be tested with resistance mode to confirm they are not leaking.

Sorry, was a bit busy but now have time to work on this board again.
ACN 8Ohm
ACP 8Ohm

I removed both mosfets from the board and they work normal and show no strange behaviour. Onboard i only get 6 MOhm. With second mosfet removed i get 20v on drain and source of first fet. When both are onboard only 20v on drain of first and nothing else.

[mon2]

Yes. What is the resistance to ground of ACN? ACP? This is the main power rail. Testing if it is shorted.

Also the ACDRV voltage should be ~25v to enable so the dcin mosfets are also suspects. If the main power rail is not shorted then the dcin mosfets are to be tested with resistance mode to confirm they are not leaking.

[dbuergi]

Suggest to place back the original JB2 diode. Not clear on the full details of this JB2 diode and also the internal orientation of the potential dual diodes. That, if this part is with dual diodes, the anode to cathode placement inside will matter.

With the original JB2 diode, do you have 2v7? Also, remove all power -> meter in diode mode. Where does the single pin on this JB2 diode travel to on the board?

No i only get 2,74v with the diode removed. With the diode i get 1,7v and 20v on drain of first DC mosfet. Removed i get 2,74v and the mosfet is pulsing under the thermal cam but there is not anything getting through it. Single pin has 4v and goes to the 822 resistor(one side 4v and other 20v).
I also made some more measurements on the BQ chip:
VCC 20v
ACDRV 0v
ACOK 0v
ACDET 2,74v
REGN 6v
CMPIN 0,3v
BATSRC 0,5-0,7v pulsing
BATDRV 0,155v
BATSRC 0,155v
SRV 0,155v
CMSRV 0-0,54v pulsing

Top right pin of the diode also shows 0,155v when it's on the board and 0v when removed.
So maybe my problem is somewhere in the battery path? Or maybe since CMPIN is too low the fault is somewhere in ACP /ACN/Shunt?

[mon2]

Suggest to place back the original JB2 diode. Not clear on the full details of this JB2 diode and also the internal orientation of the potential dual diodes. That, if this part is with dual diodes, the anode to cathode placement inside will matter.

With the original JB2 diode, do you have 2v7? Also, remove all power -> meter in diode mode. Where does the single pin on this JB2 diode travel to on the board?

[dbuergi]

Oh Measure the resistance to ground of ACDET pin. No power to the board during this test. What is the exact resistance at this time?

Hello mon2,

maybe you have any more hints or ideas? I replaced the JB2 which is a BAV99W but the behaviour went back to my 1,7v and no more pulsing on first fet. :-/

[dbuergi]

Okay maybe i got the right twist now. Since i have 20v and 0,7v on the 822 resistor something is dragging down on the other side and this point goes to the battery area.
The diode on my pic shows voltages in every direction and i have a e7ej tantalum cap (not tue one one my pic) next to the battery connector which is the only one one the Board with no continuity. So could this be the cause?
Any information about the precise specs for the diode?

Finally some news. I unsoldered the JB2 ?diode? and finally got my 2,7v on pin 6 back.
But! the board is still not working. At the moment i can see that the first DC mosfets tries to switch and stops and does this in a loop. My guess is that it could be a reverse protection diode or p channel mosfet and without it there is no final go. So any ideas on this theorie and maybe anybody can help with replacement identification?
Also second mosfet (was also replaced to test if behaviour changes) is still showing 0,49v and 1,3v and has 2 Ohm on source. But it's connected to system rails and voltage injection didn't show any shorts.

[dbuergi]

Oh Measure the resistance to ground of ACDET pin. No power to the board during this test. What is the exact resistance at this time?

Okay maybe i got the right twist now. Since i have 20v and 0,7v on the 822 resistor something is dragging down on the other side and this point goes to the battery area.
The diode on my pic shows voltages in every direction and i have a e7ej tantalum cap (not tue one one my pic) next to the battery connector which is the only one one the Board with no continuity. So could this be the cause?
Any information about the precise specs for the diode?

[dbuergi]

Oh Measure the resistance to ground of ACDET pin. No power to the board during this test. What is the exact resistance at this time?

19k Ohm

[mon2]

Oh Measure the resistance to ground of ACDET pin. No power to the board during this test. What is the exact resistance at this time?

[dbuergi]

Good on the new ACDET voltage. This range is now OK. Carefully, measure and post the voltage on each pin of this charger IC in a table for a review. Be sure to include the pin # and their function else it is more difficult to compare against a known good charger IC.

Ah sorry my description was bad. I meant 2,7v with the calculator and my replaced resistors. Problem still is the same with 1,7v on pin 6. :-/

[mon2]

Good on the new ACDET voltage. This range is now OK. Carefully, measure and post the voltage on each pin of this charger IC in a table for a review. Be sure to include the pin # and their function else it is more difficult to compare against a known good charger IC.

[dbuergi]

I forgot to mention that 43T next to the 10 Ohm resistor should be the BAT54CW from your second pic. Diode mode shows normal values. I also changed my high and low side resistor with same values (high 127k and low 20k). I`m coming out at 2,7v or is the tolerance too big with 0,3v and needs to be adjusted? Normally between 2,4 and 3,1v should be fine.
I marked everything in the picture. Any other ideas?