Asus X1403ZA rev 2.1 no power short on main

[johnbeton]

Hello,

I have an Asus X1403ZA board. Came in with no power or charge light. One screw of the hinges let loose and was dancing around inside the laptop.
I have 19v coming in the first mosfet, but nothing on the source or gate. (also no voltages on other rails, no shorts on coils)
The current resistor and source of the second mosfet are short to ground. I have looked for schematic or boardview, but nothing to be found.

Anyone have tips where to start ?

[shiyab]

5V &3V CHEK

[mon2]

Review the topside markings of the DCin mosfets and also the nearby charger IC. Post each of these details for a review.

Post pics of your logic board where you are noting the first mosfet to save on some time against the review of the boardview file.

From the BV review,

PU8901 BQ24800RUYR//TI is the charger IC.

PQ8901 & PQ8902 DCin mosfets are the suspects. Carefully flux and remove the 2nd DCin mosfet.

Check this removed mosfet after it is cool and on your work table. Likely it is defective.




Here is the link for the BV file for this board:

Asus X1403ZA Boardview file - Badcaps

[johnbeton]

i have no 5v or 3v

PQ8901 and PQ8902 are E180AJ
PU8901 is BQ24800TI 258 A1J3
I removed the second mosfet. From Source to drain I have 1.8Oms resistance, from Source to gate and drain to gate no continuity.
After removing the second mosfet still 0v after 1st mosfet

[shiyab]

19 V CHEK
FULL

[mon2]

Is the 1R8 ohm's resistance measurement of the removed mosfet that is on your work bench? Or is this the measurement of the pcb pads on the logic board after removing the 2nd dcin mosfet?

continue to measure the resistance of the first dcin mosfet that is on your logic board.

measure:

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

post each measurement. No power during these checks.

[johnbeton]

The 2nd mosfet was measured on the mosfet itself on the bench.

These are the measurements on the 1st mosfet (still on the board, 2nd mosfet is still removed):

source (1-2-3) & drain (5-6-7) = 167 Ohm
source (1-2-3) & gate (4) = nc
gate (4) & drain (5-6-7-8) = nc

[shiyab]

Is the 1R8 ohm's resistance measurement of the removed mosfet that is on your work bench? Or is this the measurement of the pcb pads on the logic board after removing the 2nd dcin mosfet?

continue to measure the resistance of the first dcin mosfet that is on your logic board.

measure:

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

post each measurement. No power during these checks.

19 V CHEK THEN 5V&3V

[johnbeton]

Hello Shiyab, I checked 19V, it is present before 1st mosfet, but not after.
No 5V or 3V present.

I have been trying to follow the traces by the boardview. I notice very low resistance to ground on AC_BAT_SYS (12 ohms). Is this something ?

[mon2]

The first mosfet also appears to be shorted. Remove it and confirm the same resistance measurements. Both mosfets will need to be replaced but first need to check if there are other shorts in this area of the logic board.

[johnbeton]

OK, removed both mosfet, now I have no NC on the board in every combination (D S G)
I tested both mosfets on the bench with the multimeter in Diode-mode. Both have the same result: I have open circuit from Source to Drain, and NC on all other combinations.

[mon2]

Requested resistance (not diode) measurements so we can compared against other mosfet readings. A low resistance measurement means the mosfet is shorted. The 1R8 = 1.8 ohms is a short on the mosfet from the removed 2nd mosfet.

Continue to check in resistance mode the PCB pads where these parts used to be onboard. That is, check the resistance to ground of the source (1-2-3) to ground; then gate (4) to ground; then drain (5-6-7-8) to ground.

Post each measurement. Again, if there is a low resistance measurement on any of these PCB pads, then there may be a shorted component onboard that needs to be reviewed.

[johnbeton]

Ok, i did wrong the previous time, here are the measurements on PCB Pads:

1st mosfet
Source - GND: NC
Gate - GND: NC
Drain - GND: 68.2k

2nd mosfet:
Source - GND: NC
Gate - GND: NC
Drain - GND: 12 ohms

[mon2]

The 12 ohms to ground means that you have a shorted part on this main 19v rail. Would you have an adjustable power supply?

need to use it to inject 1 volt (no higher) at 3-5amps onto this rail. Then inspect on who is heating up.

[johnbeton]

Yes, I have a power supply, I injected 1 volt, at first 3amps then went up to 5amps (rail is pulling around 0.9A). I injected this on the drain of the 2nd mosfet. But nothing getting hot or even warm. I can only test with feeling around and using IPA.

[mon2]

Check the heat from the CPU / PCH without the heatsink.

[johnbeton]

the cpu and PCH don't warm up, not even a little bit.
On inspecting all components in AC_BAT_SYS, I noticed PJP8102 looks like it is pressed down a little bit, maybo from that screw, I dont' know.
Could it be possible this is short to ground from a trace underneath ?

[mcplslg123]

Keep injecting 1V/5A for 15 mins and then see if any area is slightly warm.

[shiyab]

Hello Shiyab, I checked 19V, it is present before 1st mosfet, but not after.
No 5V or 3V present.

I have been trying to follow the traces by the boardview. I notice very low resistance to ground on AC_BAT_SYS (12 ohms). Is this something ?

chek mosfet get voltage then ok change the mosfet
chek mosfet out put shor or normal

[johnbeton]

I injected 1V/5A for about 20 mins, the cpu feels a little bit warmer than the rest of the board. No other components feel warm.
IPA on CPU vaporises very slow, but little faster compared to other areas.
So this is probably end of story ?