ASUS G751JY nvvdd not turning on

[myth77]

The laptop turns on but nothing on the screen. I checked every part of the motherboard and everything is fine except NVVDD is not turning on, no voltage after G_PWR_SRC_NVVDD mosfets, they are not turning on. I borrowed two same working motherboards and cheched resistence on all the DGPU nets and only difference i found was on FBVVDQ...On working motherboards the resistence is arround 90 ohm, and on not working its arround 38 ohm...but the funny thing is that on FBVVDQ net the voltage is present.

So...questions...the lower resistence on FBVVDQ net indicates that one or more gpu memory moduls are bad? if so, how to determine which one?
And why NVVDD is not turning on? is it because FBVVDQ is bad? I couldnt find anywhere what is the power on sequence order...which is first? fbvvdq or nvvdd? and are they depending on each other to turn on?
Help please
Boardview attached.

[caspian]

Re: ASUS G751JY nvvdd not turning on

Leave FBVDQ alone and focus on NVVDD to fix. how much resistance on PL8501?

[myth77]

Re: ASUS G751JY nvvdd not turning on

arround 9 ohm...it is the same as on the working motherboard

[myth77]

Re: ASUS G751JY nvvdd not turning on

Update...
I was comparing two motherboards, one working one not working, plug the charger, used a multimeter...and going step by step...
first of all i found datasheet for PU8501 pwr controller UP1661P for nvvdd. i checked the voltage on first pin and yes i had on both motherboards...second pin, the one that should open mosfet no voltage on not working motherboard. Then i checked the third pin (enable pin p-nnvdd_en) and only 0.5v reading. On working one it is arround 3v. Also same on fourth PSI pin...


So i was going back throught the boardview...why the P_NNVDD_EN_10 is not receiving/trasnfering voltage...so i go through the boardview...and came across this area...as far as i can see through this mosfet q7101 and 0 ohm resistor R7130 should power P_NNVDD_EN_10 and pwr controller..but on working motherboard i have voltage on that second mosfet pin and dgpu_pwron network but on not working i dont have, i have arround 13 v on pins 5 and 6- DGPU-DSG-SW


And from here i am lost...can someone take a look on boardview and suggest what/where to check next?

THank you very much

[caspian]

Re: ASUS G751JY nvvdd not turning on

what voltage on pin 2 and 3 of Q7101?

[myth77]

Re: ASUS G751JY nvvdd not turning on

both 0V, on pin 2 and pin 3 ther is 0V.
Pin 5 and 6 DGPU_DSG_SW 13.5V

[caspian]

Re: ASUS G751JY nvvdd not turning on

now measure voltage on all pins of Q7105.

[myth77]

Re: ASUS G751JY nvvdd not turning on

pins 5 and 6 (DGPU_DSG_MAIN) 13,4v,
pin 3 DGPU_PWR_ONMAIN 0v,
pin 2 N43278125 0,05V

[caspian]

Re: ASUS G751JY nvvdd not turning on

are the other voltages the same as you reported on the following thread?
www.badcaps.net/forum/showthread.php?t=65496

[myth77]

Re: ASUS G751JY nvvdd not turning on

Yes.

[caspian]

Re: ASUS G751JY nvvdd not turning on

It would be better if you continued the old thread. you mentioned: 0.1v on 3v3_aon net,
If so, many voltage rails cannot be present on the board. please measure 3v3_aon again.

[myth77]

Re: ASUS G751JY nvvdd not turning on

It would be better if you continued the old thread.

yes, you are right, sorry

you mentioned: 0.1v on 3v3_aon net,
If so, many voltage rails cannot be present on the board. please measure 3v3_aon again.

i double checked +3V3_AON is 0.09V

[caspian]

Re: ASUS G751JY nvvdd not turning on

How much voltage and resistance on PL8001 and PL8200?

[myth77]

Re: ASUS G751JY nvvdd not turning on

NOT WORKING MOTHERBOARD:

PL8001 i have arround 60 ohm and 1.7V

PL8200 i have arround 85 ohm and 1.08V

WORKING MOTHERBOARD:

PL8001 i have arround 80 ohm and 1.77V

PL8200 i have arround 113 ohm and 1.08V

[caspian]

Re: ASUS G751JY nvvdd not turning on

do the CPU and PCH get warm on the faulty mainboard?

[myth77]

Re: ASUS G751JY nvvdd not turning on

yes, they are getting warm.

[caspian]

Re: ASUS G751JY nvvdd not turning on

probably, either CPU or PCH is faulty. CPU is the most probable. I wish it was not soldered to the board.

[myth77]

Re: ASUS G751JY nvvdd not turning on

when i say warm i dont mean like really hot, i can touch it with finger and sense the heat, but not overheating...
Also, can i measure resistence on pch and cpu to ground and compare the measure with working motherboard? is it enough to conclude that cpu/pch is working?
Also, can you explain it to me what part turns on +3v3_aon? i checked every part of the aon net and i cant figure what resistor/pwr/mosfet...transfers volts to +3v3_aon?
Thank you!