Asus GA401QM dead, no lights.

[jacobtc]

Yes, I know I had a similar laptop I fixed a while ago, don't blame me for picking up a new (dead) one

This one shows no life with AC or USB-C charging. Reset CMOS, removed battery, and tried again, nothing. No lights, and no response when power on button is pressed.

Measured DC In mosfets as good, and the board seemingly seems to supply 20V, 5V and 1.2V with my quick measurements. Battery is completely depleted, I believe this has disabled itself as my other battery also did. When DC is plugged in the GPU gets 45C and CPU VRM/Mosfets get to same temperature. CPU itself is cold.

No immediate shorts on the board as I could find, but will need to dig deeper later.

Coils at CPU area measure 30-40ohm.

The laptop is shipped with liquid metal on the CPU, and the cooler screws had been used, so the first thing I checked was for any leakage of the LM on the board, but I haven't found any.

I have attached some pictures of the board.

What would be the correct way to tackle this board? Haven't had a board with no immediate short to correct.

[mon2]

Re: Asus GA401QM dead, no lights.

See attached.

The mosfets mated with the charger IC need to be reviewed. While they are passing through the voltage to the logic board, you may have defective mosfets.

Start with, remove all power / no battery.

Meter in resistance mode.

Measure the resistance of each of the 2 x dcin mosfets 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 and the meter scale used.

Repeat for the next mosfet.

[jacobtc]

Re: Asus GA401QM dead, no lights.

See attached.

The mosfets mated with the charger IC need to be reviewed. While they are passing through the voltage to the logic board, you may have defective mosfets.

Start with, remove all power / no battery.

Meter in resistance mode.

Measure the resistance of each of the 2 x dcin mosfets 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 and the meter scale used.

Repeat for the next mosfet.

Thank you for your continued support!

PQ8901:
S-D: 300kOhm
S-G: 2.5Mohm
D-G: 5.6Mohm

PQ8920:
S-D: 1.8Mohm
S-G: 2.6Mohm
D-G: 5Mohm

Meter scale on Auto.

Thanks!

[mon2]

Re: Asus GA401QM dead, no lights.

To me, PQ8901 with the 300k ohm resistance, being low, is a suspect. Worth a replacement so that it can be as high as the 2nd mosfet.

Measure very carefully and post the voltages on the charger IC (PU8900) with the adapter connected. For now, leave off the battery.

Also, review the voltage on each coil with the adapter connected.

Any coils with no voltage or a low voltage ?

[jacobtc]

Re: Asus GA401QM dead, no lights.

To me, PQ8901 with the 300k ohm resistance, being low, is a suspect. Worth a replacement so that it can be as high as the 2nd mosfet.

Measure very carefully and post the voltages on the charger IC (PU8900) with the adapter connected. For now, leave off the battery.

Also, review the voltage on each coil with the adapter connected.

Any coils with no voltage or a low voltage ?

It must have been a mistake from my side, double checked, and PQ8901 now shows the same Mohm resistance as PQ8902.

The two coils on the right side measure very low or none. Left side coils measure fine at 3v3, 5v, 1.8 etc.

See attached.

I have also attached some thermal images of the whole board, and the individual coils at CPU area, and of the GPU.

Charging IC measures:
20V on ACC
6V on ACOK
26V on ACDRV
20V on CMSRC

So it seems fine?

[mon2]

Re: Asus GA401QM dead, no lights.

Voltages & revised resistance look ok.

Lower coil = battery charge coil so ok that it has no voltage since the battery is not connected = coil PL8901.

Other coil is PL9301 = secondary battery charger ?? (according to the schematic) - so this logic board has support for 2 x batteries ?

[jacobtc]

Re: Asus GA401QM dead, no lights.

Voltages & revised resistance look ok.

Lower coil = battery charge coil so ok that it has no voltage since the battery is not connected = coil PL8901.

Other coil is PL9301 = secondary battery charger ?? (according to the schematic) - so this logic board has support for 2 x batteries ?

Should I connect battery and check coils again?

It only has a single battery, no support for 2 batteries.

[mon2]

Re: Asus GA401QM dead, no lights.

Yes, connect the battery and then check these coils again. At least one should pass through the battery charge voltage for your attached pack.

[Sephir0th]

Re: Asus GA401QM dead, no lights.

I'd be more worried about how the GPU warms up with even no 3.3V present, since DC-IN seems to work perfectly fine. I'd like to know which voltages you measured where.

[jacobtc]

Re: Asus GA401QM dead, no lights.

I'd be more worried about how the GPU warms up with even no 3.3V present, since DC-IN seems to work perfectly fine. I'd like to know which voltages you measured where.

3v3 is present, where did I say otherwise?

[mcplslg123]

Re: Asus GA401QM dead, no lights.

Do you have a dc supply?? It seems to me the mb is indeed getting turned on but partially as you do have 1.2V rail. VCCSA present??

[jacobtc]

Re: Asus GA401QM dead, no lights.

Yes, connect the battery and then check these coils again. At least one should pass through the battery charge voltage for your attached pack.

Sorry, just remembered that the battery pack is completely dead (0V). I mentioned this in OP, so it won't really give any voltage to the coils. I checked the coils and they show the same. I do have a known good battery, but I am scared that what killed the original battery, will kill the good battery. I already have two of these dead batteries lying around, so it seems like this is a common issue.

[jacobtc]

Re: Asus GA401QM dead, no lights.

Do you have a dc supply?? It seems to me the mb is indeed getting turned on but partially as you do have 1.2V rail. VCCSA present??

Yes I do. I don't know where VCCSA is generated.

[jacobtc]

Re: Asus GA401QM dead, no lights.

Could this be a dead CPU? How would I check that? The coils around the CPU has a low resistance, but thats normal, right? They are about 30 Ohms.

[mon2]

Re: Asus GA401QM dead, no lights.

30 ohms is not a low resistance for CPUs. We thought we had one last week (Macbook A1398) where the resistance was 0.9-1 ohms. Working fine.

[jacobtc]

Re: Asus GA401QM dead, no lights.

30 ohms is not a low resistance for CPUs. We thought we had one last week (Macbook A1398) where the resistance was 0.9-1 ohms. Working fine.

Well, then I'm lost, all voltage is there, but CPU won't turn on it seems. Or so I guess, everything else gets varm, but not CPU.

[Sephir0th]

Re: Asus GA401QM dead, no lights.

3v3 is present, where did I say otherwise?

Missed the Post where you have mentioned the other voltages present. Sorry for that.

30 Ohms sounds pretty high for VCC Vore supply, though. Even when it is a AMD System. We have a Ryzen 7 soldered there. Are you sure each of the 5 coils to the right have the same value? Measurements are still to general to get a clue what is where and especially what's going on.

[jacobtc]

Re: Asus GA401QM dead, no lights.

Missed the Post where you have mentioned the other voltages present. Sorry for that.

30 Ohms sounds pretty high for VCC Vore supply, though. Even when it is a AMD System. We have a Ryzen 7 soldered there. Are you sure each of the 5 coils to the right have the same value? Measurements are still to general to get a clue what is where and especially what's going on.

I'm new and still learning, I think its better to get a feeling of how stuff works by just throwing myself at it, and sounding like an idiot for the first year or two

When measuring the coils I am using a screw hole as ground, should measurements be done on each side of the coil? See attachment.

[Sephir0th]

Re: Asus GA401QM dead, no lights.

No offense, but something must be wrong with the probes our your multimeter. From typical design of these boards, the 5 most left coils are for GPU Core and I wouldn't expect really more than 1 Ohms to GND there. 5 coils to the right should be related to CPU but maybe different rails in addition.

Someone should correct me otherwise.

Edit: Screw hole might be okay, but pay attention to proper contact. One side of each coil is enough, since they're basically a "wire".

[mon2]

Re: Asus GA401QM dead, no lights.

Short the probes on your meter. What is the resistance that is shown ? It should be ~0 ohms.