Asus laptop motherboard A15HC Rev:2.1

[Andreasbest]

Hello mates!
Today i received a completely dead laptop (no leds at all) i only measure voltage to the charger connector on motherboard.
Motherboard is A15HC and unfortunately no diagram is available so i'm kinda blind.
Took some photos of the area around input in case you can help me a while.
In case you need pictures of another area let me know, i have the board on bench.
Thank you in advance!

[caspian]

Re: Asus laptop motherboard A15HC Rev:2.1

measure voltage on all pins of the 8-pin transistor which is located near J6001 in the first photo.

[subroto]

Re: Asus laptop motherboard A15HC Rev:2.1

Check 19V in SOURCE first MOSFET above R020. Let me know then.

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

First, thank you very much for helping me.
Second, the MOSFET has 19.5v on all pins except pin 4 that has 9.7V.

[BlueMidnight]

Re: Asus laptop motherboard A15HC Rev:2.1

What you measured appears to be a P-channel input MOSFET, and 9.7V on the gate means it has been switched on. Since that input MOFSET is right before the current sense resistor, you must have 19V on the main power rail.

Next, measure the 2 grey coils/inductors near the USB ports. Those are for the 3V and 5V rails. If either voltage is missing, measure all pins on the controller chip located on the reverse side of the board near the coin cell battery, check for shorts from the coils to ground, and feel if the controller chip is getting hot. Also, find out what the part number is on that chip.

[JaroTech]

Re: Asus laptop motherboard A15HC Rev:2.1

Hi, find the BD9528 (32-pin chip) and measure the voltage on pin 4 (EN2), pin 9 (CTL) and pin 21 (EN1).

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

Hello again Blue!
The grey coils hve 3.3v input and output the left and 5v input and output the right one.Until here everything look fine.

Hello too Jaro.
The pin 4 has 3.3v
The pin 9 19.5v
and the pin 21 3.3v

[JaroTech]

Re: Asus laptop motherboard A15HC Rev:2.1

You can continue to solve your problems with BlueMidnight, he is more experienced than me.

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

Thank you for coming Jaro.If you have any ideas let me know anytime

[BlueMidnight]

Re: Asus laptop motherboard A15HC Rev:2.1

Looks like there is a boardview available for rev 2.0 of the board, so hopefully there aren't many differences.

BoardViewer will be the easiest way to view it. Just type names of nets/signals on the box at the top to find the relevant components in the list in the net tab on the right. And from there you should should be able to find good places to measure them.

The power sequence looks very similar to the attached image. But be aware that it is for a different board, so some slight differences do exist. But at least it's from the same manufacturer, so it has the same names for most things.

- SUS_PWRGD should be 3V
-+12VSUS power rail should be... well.. around 12V
- PM_RSMRST# should be 3V
- PWR_SW# should be 3V, go to 0V when power button is pressed, and then go to 3V again
- PM_PWRBTN# should do the same thing as PWR_SW#
- Then PM_SUSC# should go to 3V
- Then PM_SUSB# should go to 3V

Once you figure out the power sequence step it's not getting passed, you can examine the related circuits more closely.

I'm working now, but I can follow-up later with more detail on where to measure these things if needed.

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

Unfortunately boardview file contains a chinese program and a BMP file that cannot opened by Boardviewer.
Found the files elsewhere.Check them now for the points you told me.

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

If we assume that where cross=checkpoint then these are the results
SUS_PWRGD is 3.3v
+12VSUS is 13.9v
PM_RSMRST# is 3.3v
PM_PWRBTN# is 3.3v
PM_SUSC# is 0v
PM_SUSB# is 0v

[BlueMidnight]

Re: Asus laptop motherboard A15HC Rev:2.1

I should have been more clear. The linked post had 2 downloads. The second one ("Pegatron A15HC r2.0 boardview.rar") is the boardview. The first one ("ASUS_TSIC.zip") is a program to view it. However, the one at boardviewer.net is much much better. But I'm glad you got it working.

PM_RSMRST# and PM_PWRBTN# being 3V is good. But you also have to make sure they change to 0V for a second when you push the power button. That will tell us if the EC and PCH are not getting the power button signal or if they are getting it but just not acting on it.

PM_SUSC# and PM_SUSB# being 0V tells us the board is not getting passed the power button step.

Also, when you said in your first post that it has no lights at all, does that include the battery charging light? In other words, when the battery and the AC adapter are both connected, is there still no light showing that the battery is charging/full?

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

PM_PWRBTN and PM_RSMRST doesn't change to 0 when i press the power button.
Yes even with battery connected, no led at all.

[BlueMidnight]

Re: Asus laptop motherboard A15HC Rev:2.1

Wait.. that was a typo. I meant to say PWR_SW# and PM_PWRBTN#.
PM_RSMRST# is fine. You haven't mentioned measuring PWR_SW# however.

PWR_SW# is connected directly to the power button, so that one better change from 3V to 0V and back to 3V when you pressed the button. If it doesn't, then there's something wrong with the button or that circuit. If it does, then there may be something wrong with the EC or the EC firmware.

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

You are right, i forgot it!
PWR_SW has 3.3v and gets to 0 when i press the power switch.

[BlueMidnight]

Re: Asus laptop motherboard A15HC Rev:2.1

Okay, so PWR_SW# is working. If possible, you may also check SUSCLK with an oscilloscope or a frequency counter to make sure it's 32.768kHz.

Hmm yeah this is looking like it's probably a firmware issue (assuming no bad solder joints or other weird problems). The EC is receiving the PWR_SW# signal, but not relaying it to the PCH (via PM_PWRBTN#). I don't personally have a copy of this firmware, but I see it's out there on the non-free sites at least.

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

I see.
But what is the EC mate?

[BlueMidnight]

Re: Asus laptop motherboard A15HC Rev:2.1

The Embedded Controller. These kinds of chips were originally called a Keyboard Controller (KBC). But then more functions were added and it became the Super I/O (SIO). Now it's just called the Embedded Controller, and the KBC and SIO are just sections inside of it. People still use the old names sometimes though.

It's typically the largest chip on the board other than the CPU and PCH. It controls all the simple board logic such as the keyboard, LEDs, fans, power button, and the first parts of the power-on sequence.

On the A15HC it is a Nuvoton brand (NPCE794LA0DX I think). Other common brands include ITE and ENE.

The EC has its firmware, and the system has it's firmware/BIOS/UEFI. On some boards the EC and system firmwares are stored on the same ROM chip. On some boards they are on separate ROM chips. And on some boards the EC has internal flash memory to store its own firmware, while the system firmware is alone on a separate chip.

The A15HC stores both firmwares on the same chip. It's an 8 pin Winbond chip (as they almost always are) that is located near the coin cell battery.

[Andreasbest]

Re: Asus laptop motherboard A15HC Rev:2.1

I see.
And how can it be flashed since motherboard is dead?
External programer?