Laptop Zenbook UX480 Fuse L

[Sephir0th]

Re: Laptop Zenbook UX480 Fuse L

My friend, you have to clarify whether the board works as expected without battery present. If not, there is no point to troubleshoot a battery issue right now, since the Charging controller works like expected from measurements.

You have to understand, that the device follows a sequence. All power rails are supposed to come in a predetermined order. If you finally start to look at the whole board, instead of concentrating on random points, experienced members here might be able to tell where to look at.

At this point the only thing we know is, Main power rail, 3.3V and 5V supply is present. that's not much and not sufficient to troubleshoot a motherboard.

Maybe i'm wrong and the board is working. Please clarify.

[corrize]

Re: Laptop Zenbook UX480 Fuse L

I know a little bit the sequence and how to the first components works, mosfets, charging chip (open or close mosfets and drive mosfets for charging battery), and the 3.3v-5v chip.
I supposed if these components worked, the next step was the superIO chip wich waiting start signal from power button.
But I’m knowledge seeker, I expected if mosfets, charging chip and 3.3v-5v chip working, at this step, the battery can charge, even if the superIO or other chip has an issue. Because I supposed the charging chip is independant for manage the battery charging, but I guess I’m wrong.
And I don’t know wich chip manage the light (charge and power).

I have no simplified schematics of the sequence. If you have, it is welcome.

[Sephir0th]

Re: Laptop Zenbook UX480 Fuse L

You somehow managed to repeatedly not answer the question, whether the board fully works without charger only or not. For this reason I can't ask the necessary questions.

And regarding the EC, when 3VALW/5VALW are present, there is usually no point to check around the EC, since at this point it is already running and has (de-)asserted a few signals. They can fail in this state but that's a really rare case.

[corrize]

Re: Laptop Zenbook UX480 Fuse L

I don’t know if the laptop works only with battery (and without adapter), because the battery is empty. But it’s a good idea to test with only battery.

The diagnose is in stand by, I’m waiting the new resistor for replace the dead one. This resistor is close the ram memory power chip, so the ram should not be able powered. Will see after replacement.

Nice to learn the EC works (it’s a bga one).

[Sephir0th]

Re: Laptop Zenbook UX480 Fuse L

Well, finally there was a Spelling mistake by myself. I have meant "with charger only".

[corrize]

Re: Laptop Zenbook UX480 Fuse L

OK, as I said above, with adapter only, no light, no sign of life, nothing after pressing power on button, (and battery don't charge).

[Sephir0th]

Re: Laptop Zenbook UX480 Fuse L

Without power present, check resistances to GND of each power rail on your board (of the working power rails too!).

If you don't know the designation of the various power rails, take a picture of the board and write the values near the coils.

[corrize]

Re: Laptop Zenbook UX480 Fuse L

I replaced the resistor, but no change.
So, the diagnose can continue.

I summarize :

On this board, I saw 3 different issues :
1 - the first « true » issue : a capacitor shorted close the CPU VRM dual mosfet.
2 – oxydation (close DC jack mosfets)
3 – the owner tryed to unplug the LVDS connector without disconnecting the battery, and that burned the connector and the fuse

I plugged the laptop (without battery) : no light, nothing.
When I press the power button : the same, no reaction
19v ok at first mosfets, and 24v at gates
+5v and 3.3v présents
charging chip seams to be good

With adapter and and battery (empty) plugged, no charging. At the coil closest : 0.86v, it should be 12v ou 15v (battery charge voltage).
Battery only : not tested : the battery is empty

See the attached picture with measurments at coils (graphic chip VRM at 1.2 Ohms is very low but not shorted).

I supposed a corrupted bios but no light at all when I press the power button, so I don't know ?

[corrize]

Re: Laptop Zenbook UX480 Fuse L

I add, on picture, all coils without measurments are 0v. So only 3 coils have voltage battery coil : 0.86v, and 5v and 3.3v.
Do you see something weird or all is normal pls ?

[corrize]

Re: Laptop Zenbook UX480 Fuse L

Update : I replaced bios and I saw for the first time the charging LED on, and when I press the power button, the power LED on. So that was a bios issue.
But now, even with the power LED on, the laptop don’t start, all coils are 0v (except 3.3v 5v and 1.8v), (I don’t plugged the battery).
I have not yet started a new diagnose.
Before, I wanted to ask you if that could be a corrupted or bad bios or not pls ? Because I have no experience of bios issues.

[corrize]

Re: Laptop Zenbook UX480 Fuse L

Update : since the last time, I recovered 1.05v at PCH coil.
So, the voltages that was present : 3v, 5v, 1.8v and 1.05v.
« Was » because I replaced the ram memory driver chip (richtek 5E=) because oxydated and I loosed 19v rail. Now, the resistance at DC jack shunt resistor is something like 182 Ohms, the same as the ram memory coil.
I checked ; I have 0 Ohms between DC jack shunt resistor and the ram memory coil, so continuity.
That’s means the 19v was able to reach ram memory ?

I can’t understand how it is possible ? What can be dead between shunt resistor and ram memory coil ? The ram memory driver chip ? The dual mosfet ?