Asus UX31E rev 3.2

[dvorel]

Hello,

I have issue with ux31e, after pluging charger in power, caps and f2 lights come on and off in intervals. I measured all voltages are fine except VRM PWRGD, it jumps from .1V to zero in same intervals. Vcore gets to 0.1v also and GFX core stays at 0v.

I did try to reflash bios but everything is same after it.


Thanks for your help!

[mon2]

Re: Asus UX31E rev 3.2

Power down. Remove battery.

Meter in resistance mode (200 ohms).

Check the resistance to ground for each inductor (large grey in color). Red meter probe on the coil, black meter probe to ground.

Post the details of the coils with a low reading.

[dvorel]

Re: Asus UX31E rev 3.2

Power down. Remove battery.

Meter in resistance mode (200 ohms).

Check the resistance to ground for each inductor (large grey in color). Red meter probe on the coil, black meter probe to ground.

Post the details of the coils with a low reading.

Here are the measurements.

PL8200 -> 32.2ohm
PL8003 -> 15.5ohm
PL8700 -> 54.8ohm
PL8005 -> 17.2ohm

And the rest (above 200ohm).

PL8800 -> 150kohm and going up
PL8100 -> 9.5kohm
PL8101 -> 5.6kohm
PL8301 -> 460ohm

[mon2]

Re: Asus UX31E rev 3.2

Hi. The coil resistance values look ok to me. They are not super low which would have indicated a short condition on the specific coil / power rail.

Are the posted readings for each and every coil on the logic board ?

Unfortunately do not believe there are schematics for this logic board but the next suggestion is to review the voltage rail for Vcore.

Can you trace which mosfets and power supply IC is used for this function ? - - IGNORE - can see them on the boardview file

No liquid damage on this box ? It just started this fault one day? Post any known history.

Your power adapter is stable enough to power this unit ?

Q1: What is the board # for your UX31E logic board ? Found the boardview files for the UX31E. Do you have these ?

Q2: What is the voltage reading @ PL8700? Do you see the +0v8 rail ?

[dvorel]

Re: Asus UX31E rev 3.2

Hi,

Yes my power adapter is fine, stable 19V.

There is repair guide and boardview file for this board, I uploaded it to attachments.

Vcore only gets to 0.1V, and VRM_PWRGD is 0 to 0.1 volts also, H_CPUPWRGD is 1.05V.

No liquid damage is present, board just wont turn on.

A: 0.9V on PL8700

[SMDFlea]

Re: Asus UX31E rev 3.2

https://www.badcaps.net/forum/showth...ighlight=UX31E

[mon2]

Re: Asus UX31E rev 3.2

1) Power down. Resistance to ground on PL8005, pin # 2 ?

2) PU8000 look ok? It is generating the Vcore.

3) Investigate mosfets PQ8000, PQ8002, PQ8003 - they are also linked to this rail.

Do not have enough experience but some may say that you have a shorted CPU which is causing the excessive current draw. However, first do review the above points. Perhaps you have a shorted mosfet / shorted cap that have yet to be found.

[dvorel]

Re: Asus UX31E rev 3.2

https://www.badcaps.net/forum/showth...ighlight=UX31E

I did go through that with no luck..


1) PL8005 resistance on #2 to GND 15.2ohm

2) No, Vcore is only 0.1V

3) I think shorted mosfet would pull Vcore to GND or to 19V, and that is not happening here

EDIT: Found that PR8076 was high value, replaced It and now I'm getting Vcore around 1.1V but motherboard still doesnt turn on

[mon2]

Re: Asus UX31E rev 3.2

1) What is H_CPUPGWRGD voltage now ?

2) Voltage on PL8003 ? (+VGFX_CORE)

[dvorel]

Re: Asus UX31E rev 3.2

CPUPWRGD and VGFX are still 0v

Edit: CPUPWRGD is 3.3v for half a second and then 0V for few, same for Vcore. VGFX iz 0 all the time.

[mon2]

Re: Asus UX31E rev 3.2

Locate the power supply region responsible for +VGFX_CORE and post their details here.

PL8003 is the inductor for +VGFX_CORE but who is driving this coil ? PQ8005 & PQ8011 are also part of this puzzle. Those parts should be reviewed next. Do you know which IC is driving these mosfets ?

In the meantime, you can check the resistance to ground for each of these mosfets (power down; meter in resistance mode) to check for shorts.

[dvorel]

Re: Asus UX31E rev 3.2

Reflashed bios one more time and got it working.

Thanks for help

[mon2]

Re: Asus UX31E rev 3.2

Excellent!

Thanks @SMDFlea.