Asus X705mb - not turning on

[lofaszjancsi]

Hi everyone,

I have an Asus x705mb at my hands, that powers on but doesn't start. I read the beginner's guide as i'm not really experienced in repairing motherboards and i can't find the board's schematic but i tried to get vcore voltage, which i'm not sure where to measure, i'll add a picture about this.

The notebook was hit hard in the middle of the keyboard, the housing shows heavy damage, but the board itself looks totally fine.
The memory used is working, i tested that in another board.
The CPU produces heat over time, and the fan is running when required.
Charging works as intended.

My first guess was the bios, so i started with searching for and writing a working dump on the chip. I attached both the original dump and the one that i tried. Unfortunately it didn't help. But caused a minor difference: with the original bios it restarts like every 10 seconds, with the new it doesn't do that.
Other than that, sata seems to have no power, usb port have, but bios crisis recovery never seem to start.

What i'd like to ask of you:
- Is the original bios ok or can anyone help me fix it?
- Schematics if anyone has
- Ideas, to continue

The board is important only, because the hard drive that was in the computer has bitlocker on it and we don't have the recovery key.

I'm not a professional, and not working in this area at all, but measuring, soldering and coding is isn't a problem and my curiosity about this is just endless.

Thanks in advance for any help!

[SMDFlea]

Originally Posted by lofaszjancsi

Hi everyone,

What i'd like to ask of you:
- Is the original bios ok or can anyone help me fix it?
Thanks in advance for any help!

Please post your bios in the "Bios Requests ONLY!" sub forum https://www.badcaps.net/forum/forumdisplay.php?f=40

[lofaszjancsi]

Sorry SMDFlea, i forgot about that rule.

Here's the link to the bios thread:
https://www.badcaps.net/forum/showth...28#post1101528

[lofaszjancsi]

I can't edit my first post, but another addition that might be interesting is, that the board powers on as soon as the charger is plugged in and cannot be turned off, it automatically turns on again. (after pressing the power button for a few seconds it seems to turn off but as soon as I release it, it starts again) if there's only the battery attached it can be turned off, it doesn't start on its own.

Also some specs:
CPU - Intel N4000
GPU - Nvidia MX110

[lofaszjancsi]

I feel a bit like talking to myself, but does anyone know what JDEBUG is good for and how it works?

[lofaszjancsi]

Based on the pinout of IT8225E found in this thread i measured a few pins that looked interesting in the pdf and in this thread

The values (when powered on):

WRST              - 3.05V
PM_RSMRST         - 3.32V
PWR_SW            - 3.01V
PS_ON             - 3.32V
PM_PWRBTN         - 0.0V (keyboard not connected, no pwr button if that matters)
AC_IN_OC          - 0V (starts at 0.07V then goes to 0.0V)
LID_SW            - 3.01V
PM_SUSB           - 0V
SUSB_EC           - 3.31V
SUSC_EC           - 0V
5VSUS_ON          - 0.0V (starts at 0.02V then goes to 0.0V)
1.2V_ON           - 0V
VSUS_ON           - 0V (starts at 1.3V then goes to 0.0V)
3VADSW_ON         - 0V
DPWROK_EC         - 3.31V
PM_PWROK          - 3.31V
PM_SYSPWROK       - 3.31V
PM_SLP_SUS        - 3.31V
3VSUS_PWRGD       - 3.23V
ALL_SYSTEM_PWRGD  - 3.28V
MP_MAXPOWER       - 1.15V

The pdf seems to contain a few values measured by the owner of that pdf, my values differ here and there.
Which values are wrong and what could be the reason?

[piernov]

Most pins are GPIO, assignment can be different between platforms. No way to know correct pinout without having schematics or boardview of the board, or at the very least a very similar one.

[lofaszjancsi]

Thanks for sharing that info. Then i'll try to test every part that i can see, i don't know what else i could do.

[lofaszjancsi]

I removed the heatsinks and checked what hardware i have, and it seems that this X705MB has 920MX somehow, i cannot find any other X705-GC030T with that video card.
the exact type of the motherboard is: 60NB0IH0-MB1010

Is it possible that the bioses that i wrote on the chip expect an MX110 (that all GC030T has based on google) and it cannot start?

[Conste]

Check all power rails at the coils

I had a similar board which had the same symptoms after a Bios Update from Windows Update. One rail was missing but I never solved the issue

Probably bad KBC flash in my case

That was my thread
https://www.badcaps.net/forum/showthread.php?t=99527

Does your unit also blink?

Does it react to capslock on/off?

[reformatt]

As it stopped working after a physical impact, then it's not likely to be BIOS. As ASUS motherboards rarely have any schematics available, I always start by a physical examination of the board under a microscope. Somethings which aren't visible to the naked eye stand out like dogs balls under a scope.

As the board has physical trauma, I would focus on the centre of the board, nudge each passive component with the tweezers to check for broken solder joints (mainly 0402/0603 components), Also check the bare copper test pads ASUS use on their boards. As they have no mask, they are the first things to get corroded, especially under the fans etc where dust may accumulate. Fixed a lot of ASUS boards with corroded test pads.

[lofaszjancsi]

Originally Posted by Conste

Check all power rails at the coils

I had a similar board which had the same symptoms after a Bios Update from Windows Update. One rail was missing but I never solved the issue

Probably bad KBC flash in my case

That was my thread
https://www.badcaps.net/forum/showthread.php?t=99527

Does your unit also blink?

Does it react to capslock on/off?

There's nothing flashing, caps lock didn't seem to react at all, when I plug the charger in, it starts, power and charging light comes on, cpu warming, cooling stars after a while but that's all. I'll check the coils.
Thanks for sharing your thoughts and experiences.

[lofaszjancsi]

Originally Posted by reformatt

As it stopped working after a physical impact, then it's not likely to be BIOS. As ASUS motherboards rarely have any schematics available, I always start by a physical examination of the board under a microscope. Somethings which aren't visible to the naked eye stand out like dogs balls under a scope.

As the board has physical trauma, I would focus on the centre of the board, nudge each passive component with the tweezers to check for broken solder joints (mainly 0402/0603 components), Also check the bare copper test pads ASUS use on their boards. As they have no mask, they are the first things to get corroded, especially under the fans etc where dust may accumulate. Fixed a lot of ASUS boards with corroded test pads.

In fact, i don't have a microscope, I'm using a magnifying glass and couldn't find anything damaged. I'll try to check everything you wrote, but my biggest fear is that something's missing from the board, that something fell off when it was hit and that'll be very hard to find.
Thanks for the help.

[lofaszjancsi]

Is it normal for ceramic capacitors (around the CPU ,under it) to show 0-1 ohm resistance to ground on one side and 20-40 ohms on the other?
Edit: also many inductors seem to show close to or 0 ohm resistance to ground

[lofaszjancsi]

1 more question, with a clean bios it does not restart on it's own, with the original bios it restarts every few mins. The CPU produces heat with both. This should mean that the CPU is executing code from it right?

[Conste]

Originally Posted by lofaszjancsi

Is it normal for ceramic capacitors (around the CPU ,under it) to show 0-1 ohm resistance to ground on one side and 20-40 ohms on the other?
Edit: also many inductors seem to show close to or 0 ohm resistance to ground

Normally all ceramic capacitors have one side on ground, so 0 ohms on one side is normal.
A low reading on the coils near the cpu is also nothing to worry about, but below 1 ohm is too low..

[lofaszjancsi]

There's nothing below 1 ohm so I guess those parts are working, I'll continue checking whatever I can. Sorry for the dumb questions and thanks for the help

[lofaszjancsi]

It seems I have finally found a dead MOSFET drain shorted to source and probably a bad ceramic capacitor near the MOSFET that seems to show infinite resistance.

[Adenitz]

Originally Posted by lofaszjancsi

It seems I have finally found a dead MOSFET drain shorted to source and probably a bad ceramic capacitor near the MOSFET that seems to show infinite resistance.

When measuring resistance between drain and source of a MOSFET and the value is small (ohms rather than k ohms), then the MOSFET is bad.
If you measure resistance of a capacitor and it is infinite, then most likely, the capacitor is good. When capacitor fails, it goes short, when resistor fails it goes to infinite resistance. Keep that in mind.

[Conste]

A question to Adenitz:

Is this measurement method also possible in circuit?
Is a mosfet not charge-driven? So it can have both a low and a high resistance between drain and source? When I tested the P channel mosfet today in diode mode a saw both open line and a small voltage between source and drain.
Could you please explain this to me?