Asus ROG N501JW - dead

[magneh]

Hi!

This is a funny one!
Board is dead no sign of life, no liquid damage.
19V are present, and I noticed a buzzing sound.

Tracked it down to the IC PU8102 PWM CONTROLLER SN51285ARUKR
TI QFN-20 , and he was also getting hot.
I also noticed I had +3VAO but not +5VAO (no short though).
Both enables to this chip are also low (0.06V something around that, also no short)
As I had this chip, I replaced it with a new one, but still the same.
Some more inspection and I found out the +3VA_EC line shorted. Injected some current and EC was getting hot. Ordered it and replaced it just a few minutes ago. short gone in +3VA_EC
Plugged the charger. same buzzing sound from PU8102...and getting hot still. Disconnected charger, measured +3VA_EC shorted again...lifted EC, short gone... had another IT8585VG chip, replaced again. No short, doublechecked.
Plugged, the charger, same thing, and +3VA_EC became shorted once again.

What could be the reason to get the EC shorted each time I plug the charger?
PU8102 is also a new chip, so kinda lost here...

Anyone could share some ideas about this?
Thanks!

[SMDFlea]

Re: Asus ROG N501JW - dead

Is that a part missing ,or liquid damage on the gate of that mosfet.

[magneh]

Re: Asus ROG N501JW - dead

Is that a part missing ,or liquid damage on the gate of that mosfet.

Yes, its a cap missing, sound related. not important.
No, just some dirt or flux.

Any ideas about this EC constant shorting?
Thanks

[piernov]

Re: Asus ROG N501JW - dead

It's right on the gate of a MOSFET for a buck converter so I doubt it is sound related and I think it may be important.

[magneh]

Re: Asus ROG N501JW - dead

It's right on the gate of a MOSFET for a buck converter so I doubt it is sound related and I think it may be important.

Sorry! my bad, I was thinking this was the cap of another ROG board I was also analysing...

This is a filtering cap for PQ9102,correct.
PC9105

But if im not mistaken, not critical, and not related with the power issue and EC constant shorting.

[jasko_jacker]

Re: Asus ROG N501JW - dead

PU8102 is a step down converter from texas Instrument TPS51285A,
If you assert that the +3VAO exist, probably (other tests should be done)
the problem is on +5VAO, try to isolate this line and check if the chip still heats up. If it doesn't heat up, you have various possibilities;
one is to inject the 5 volts on the + 5VAO line and see if any component heats up.
Each component must stay in place, even a component that seems unimportant for testing is better to be replaced.

[magneh]

Re: Asus ROG N501JW - dead

PU8102 is a step down converter from texas Instrument TPS51285A,
If you assert that the +3VAO exist, probably (other tests should be done)
the problem is on +5VAO, try to isolate this line and check if the chip still heats up. If it doesn't heat up, you have various possibilities;
one is to inject the 5 volts on the + 5VAO line and see if any component heats up.
Each component must stay in place, even a component that seems unimportant for testing is better to be replaced.

If I am remebering well I think I injected 5v into that line and very little pozer consumption...but not sure I will doublecheck tomorrow

When you mean "isolate the +5VAO line" , you mean removing the coil of +5VAO and then inject 5V?

Ill let you know as soon as I take this board out for more testing

[magneh]

Re: Asus ROG N501JW - dead

So when I assert 5V at point +5VAO the SN51285ARUKR PWM IC starts doing the buzzing sound.
I get 40mA consumption and chip does not get hot.
Ive done this WITHOUT the charger plugged in.

Ive also doublecheked and +3VAO is 3V when charger plugged in.

Ive still injected 3V at the +3VAO line, and I get 450mA consumption,buzzing sound and ITE gets hot... (without charger connected)

Any ideas of what I could do next? kinda lost with this kind of behavior...
or not worth it?

[jasko_jacker]

Re: Asus ROG N501JW - dead

If ITE is hot check for possible short or missing signals.

[magneh]

Re: Asus ROG N501JW - dead

Hello!

Ive replaced the ITE twice already, and the short goes away when I solder new chip back and plug the charger, short is back.
+3VA_EC is the line who is messed up regarding the ITE

As Ive replaced it twice with same results, what am I missing here?

[jasko_jacker]

Re: Asus ROG N501JW - dead

If the short disappears without ite so the problem probably is on the power line but not 100%, if there is a short on the +3VA_ECC (check the picture 2 and check resistence first without cut the jumper if there is a short on this jumper follow the next steps:
the +3VA_ECC came from +3VACC on SL3006 , cut this jumper to isolate
+3VA_ECC from +3VACC and check both pins ..... see pics 2

[magneh]

Re: Asus ROG N501JW - dead

If the short disappears without ite so the problem probably is on the power line but not 100%, if there is a short on the +3VA_ECC (check the picture 2 and check resistence first without cut the jumper if there is a short on this jumper follow the next steps:
the +3VA_ECC came from +3VACC on SL3006 , cut this jumper to isolate
+3VA_ECC from +3VACC and check both pins ..... see pics 2

Thanks so much for these inputs!

Just some thoughts meanwhile.
Should I first removed the shorted ITE before doing those troubleshooting steps?

But even more important, Ive just measured the signals in the repair guide near the PCH, and Ive found out ME_SUSPWRDNACK also shorted!
I suspect this short will go away if I lift the ITE, as this goes to Q3002 and to the ITE.
I think I probed this point earlier on after replacing the ITE , and there was no short.

Thanks once again for all the help

[jasko_jacker]

Re: Asus ROG N501JW - dead

You have to come up with a strategy for this repair,
Usually I try not to unsolder anything if I haven't found the problem, however at this point based on your data:
1 -> remove ite
2-> check resistance on + 3VA_EC
3-> if + 3VA_EC is in short isolate this line with precedent information.
4-> if + 3VA_EC is good, check ME_SUSPWRDNACK if this is in short,
, cut SL2212 and check short on pin 1 of this jumper
5-> if there is a short on pin 1 probably pch is dead to confirm, remove
R2213 and repeat measurement.
6-> if you don't find any short, clean well all ITE pads and power the board, measure the presence of +3VA_EC
7->if +3VA_EC is 3V , check resistence on ITE between it's GND and +3VA_EC (ite not in place) .....

[magneh]

Re: Asus ROG N501JW - dead

You have to come up with a strategy for this repair,
Usually I try not to unsolder anything if I haven't found the problem, however at this point based on your data:
1 -> remove ite
2-> check resistance on + 3VA_EC
3-> if + 3VA_EC is in short isolate this line with precedent information.
4-> if + 3VA_EC is good, check ME_SUSPWRDNACK if this is in short,
, cut SL2212 and check short on pin 1 of this jumper
5-> if there is a short on pin 1 probably pch is dead to confirm, remove
R2213 and repeat measurement.
6-> if you don't find any short, clean well all ITE pads and power the board, measure the presence of +3VA_EC
7->if +3VA_EC is 3V , check resistence on ITE between it's GND and +3VA_EC (ite not in place) .....

Thanks for all the inputs.

1 -> Done
2 - > resistance 160k oHm , diode to gnd 0.44v
4 -> resistance 615 oHm at ME_SUSPWRDNACK
6 -> First difference when powering without ITE, the buzzing sound of the PWM IC SN51285ARUKR is no longer there, but I dont have +3VA_EC

+3VACC is also 0V. isolated these 2 lines at SL3006, and I have 660k ohm at +3VACC and 340k ohm at +3VA_EC

+3VAO is 3.3V and +5VAO is 0V

[noonly]

Re: Asus ROG N501JW - dead

I have this exact problem, did you ever find a solution?

[cyngo]

Re: Asus ROG N501JW - dead

I have this exact problem, did you ever find a solution?

me too, any solutions ?

[TheWizard]

Re: Asus ROG N501JW - dead

I also have the same problem. Traced 19v front to back of board. All present. But where the 5VA0 starts i have a short. Please let us know if you have fixed this and what resolved the issue.

[mon2]

Re: Asus ROG N501JW - dead

Remove all power. Meter in resistance mode.

Measure the resistance to ground of the power rail you suspect is shorted.

Post the measurement.

[TheWizard]

Re: Asus ROG N501JW - dead

87.2 is the resistance to ground reading on +5VA0 entry point and pin 13 on SN51285ARUKR. (PU8102).

[mon2]

Re: Asus ROG N501JW - dead

@ ~87 ohms to ground = shorted component, probably a capacitor.

Do you have a DC power supply that can be dialed up to 1 volt (not higher) for injection?