Asus X555LJ somewhat alive/dead

[markuss!]

Hello!
This laptop has had a rough time by it's owner (my cousin ), I was told that it was spilled with coke several times, but how it continued to work is a mystery. Last year I was told that the laptop turned off under load and I confirmed the same thing. I had stuff to do and I left it in a corner. Months later I tried turning it on, but nothing was powering on. I took out my multi meter and I found out that the dedicated Nvidia GPU has a short to ground by putting positive multi meter probe on the GPU power coils and negative probe on the ground screw. I removed the GPU power coils, idea being that I read online it's possible to convert these laptops to only use Intel iGPU. Once I removed the coils and powered the laptop on, there was still nothing. I thought hmm, maybe I need to reprogram the BIOS. I found a similar Asus model being X555LAB, which I believe has iGPU only. I remember I took this BIOS dump from someone, who posted this dump here in these forums. I flashed that BIOS using my CH341A programmer, of course taking a dump of the original one, and once I soldered the chip back on, the laptop turned on by my surprise. Even a reboot was fine. Then I realized I needed to copy over serial number, ethernet card MAC address, windows product key. And from there everything went from working to this day I am now, where the laptop doesn't show nothing on the screen. Basically what I did I took that BIOS image, I tried to understand how to transfer the MAC address and windows product key from the dumped BIOS into the new one, but without success. I made some mistakes by booting up the laptop with some solder bridges I didn't notice. I desoldered the BIOS chip a lot of times and reprogrammed it. Then I noticed that the laptop had developed a problem, where I turned it on, it took either a long time for the BIOS screen to appear or when it did appear, the whole UI was sluggish slow. Plus when I rebooted the laptop, nothing showed up on the screen, only the backlight turned on. I also noticed that there was no boot options available, my ventoy usb didn't show up and the HDD didn't show up. These were the last signs of life I still remember the laptop had. I was thinking maybe I had killed the BIOS chip, so I ordered 5 chips from aliexpress and I put the laptop to rest. Two days ago those chips came and I took out the laptop and turned it on. Now I had nothing on the screen and laptop took a good minute to even start the fan. I thought that's strange, so I programmed a new BIOS chip, same model number as the original did, and I soldered it on. Still nothing showed up on the screen. Basically something went horribly wrong, but it's possible that maybe this problem started because of me not knowing before that the ME code needs to be cleaned, as I did flash a different model BIOS. I don't know, maybe the PCH or the EC died or there is something I missed.

Sorry for the wall of text, but I think it should help understand what component failed or I missed some step.

Have a great day and greetings!

[mcplslg123]

Re: Asus X555LJ somewhat alive/dead

What is the resistance on GPU coils?? They may not be shorted as they are supposed to be low resistance lines. Dont measure in diode mode, set your meter to 200 Ohms scale and check resistance on GPU coils.

As far as bios is considered, you may ask for clean me bios in "Bios Section" while uploading your original dump. late display may be related to dirty me region.

[markuss!]

Re: Asus X555LJ somewhat alive/dead

Hi!
I had a hard time desoldering those coils back then and I would have to find them in my parts bin, but it's possible to solder them back if they are needed for testing, but not now as of me writing this response. If it helps, right now I get 2.75ohms and -0.10ohms, because of the lead resistance, so it would be 2.65ohms on the GPU side, where the coil is supposed to be (I attached a picture, which shows where I took the measurement).
Does the ME region need to cleaned even when the bios is the original one I dumped from this laptop?

Greetings

[mcplslg123]

Re: Asus X555LJ somewhat alive/dead

2.65 Ohms on GPU coil is not short.

If original bios is used, then me cleaning is not required.Its only required when you copy bios from other working machine and try to flash it on the machine you are working now-Those cases me cleaning is a must.

[markuss!]

Re: Asus X555LJ somewhat alive/dead

I have soldered back on the GPU coils and it does the same thing what I saw a year ago when I received the board for repair. When plugging in the power cord, the fan tries to start then fails. It does that on a loop and a clicky electronic noise comes from the motherboard each time the fan tries to spin. I have the original BIOS flashed. When I removed the gpu power coils and reprogrammed the BIOS from a similar model without Nvidia GPU code, the first time motherboard turned on in windows, but again it got worse. I'm gonna guess I made the mistake of flashing a different model BIOS with dirty ME and that made the motherboard not complete POST.

[markuss!]

Re: Asus X555LJ somewhat alive/dead

I found this video on YouTube, I have the exact fan symptom as he has.
https://www.youtube.com/watch?v=d0p9PCs6qeY
Maybe the GPU is fine and I'm doing something wrong. Guy has titled the video GPU no power, so maybe there is my problem. Only thing I don't have is that he has an oscilloscope to see how things look visually.

More that I think about it, yeah this can be the problem actually. When the laptop was still working it shut off on load. Then it got worse by itself to the point, where the laptop can't turn on anymore. Maybe the GPU is fine and it doesn't get power. I need to check for more measurements.

[markuss!]

Re: Asus X555LJ somewhat alive/dead

Well I be damned, that video literally is the solution. He showed at 21:35 in video a small resistor, which has died. I found the exact spot, where is this resistor located and I noticed that the end of the resistor was gone and the pad has disintegrated with it. Maybe coke did the damage? Anyways I scrapped off just a little of the trace to reveal copper and I soldered a new resistor on. You will see how it looks in picture, one resistor is soldered at an angle. No idea if it's the correct resistor, but I'll be damned this small small component caused the whole laptop to die. I'm genuinely so amazed that I encountered my first laptop motherboard fix, which involves swapping in a new component.
Laptop just turned on in BIOS

[markuss!]

Re: Asus X555LJ somewhat alive/dead

Update - laptop doesn't work again. Laptop did boot into BIOS and I plugged in my Ventoy USB and it didn't show up. I plugged in a hard drive, no success and even a windows 7 boot DVD didn't work. After putting in a battery and plugging in the power cord, I got no boot at all. After removing the battery and plugging in the power cord, the fan doesn't even attempt to spin at all. It's like dead now.

Ideas?

[reformatt]

Re: Asus X555LJ somewhat alive/dead

Asus use long bare copper pads as test points around the boards. As they have no mask, they typically corrode after a liquid spill (or even from fan dust) and go open circuit. Any that don't have the bright copper colour, you scrape with an exacto knife to check that the pad is intact. Solder or bridge as needed. Asus have been putting a plastic membrane with adhesive on their boards now on the keyboard facing side to stop this. Not sure about this model.

If the liquid spill is big enough, and contaminated enough of the board, experience says these devices should be written off. Proper remediation is indentifying each corroded component/track/via under a microscope, repair/replace/jumper/bridge, followed by ultrasonic cleaning to remove any further contaminants. If you don't have the right tank and chemicals, I suggest writing off this board.

[markuss!]

Re: Asus X555LJ somewhat alive/dead

Yeah, I'm kinda leaning towards just calling it quits. I have left the motherboard unplugged for the whole day and checking it again, when pluggin the power cord, the laptop kicks on by itself with the fan spinning, but no screen ever shows up. Plus this laptop is in such bad shape, like the keyboard keys stick and the motherboard is yet not fixed. The IO board is also bad, as previously windows and linux didn't report any available audio device, when the laptop was still working. This laptop model is also known for having a very dumb IO board design, which connects to the mainboard using a connector, which connector goes bad. There have been multiple videos and people having problems with these X555** motherboards. I mainly wanted to try to look into deeper repair, but my knowledge mainly is with soldering, taking basic measurements with my multimeter and reprogramming BIOS chips. This is mainly for fun and my learning, as this laptop did stay in my cousins box of non working stuff for some months, but I feel this is taking so much time, that it sounds easier to find a listing for this laptop model with bad screen on used market and I could reuse this working screen.