Help with Asus Zenbook UX362F repair

[nd03]

Hello lads,

Will give a quick summary. Bought this laptop as broken. Initial board had shorted SOC (VCCGT coil shorted to GND, checked all caps and just desoldered soc to confirm, dead short from VCCGT to GND on soc). I ordered a replacement board. Board model Q326FA Rev 2.0: is: https://www.aliexpress.com/item/1005...1309180228rsDj

Installed the new board laptop booted but display was flickering very ugly in bios. Horizontal and vertical artifacts. I thought the GPU is dead but it turned out it was some almost broken wires (from previous owner) in the LVDS connector from LCD. While tampering to fix that one I probably discharged some ESD into the motherboard. I was not wearing my ESD brace and while working directly on insulated wires on the connector I touched by mistake GND with my elbow and got zapped a little (this means I was charged and I discharged some current into the motherboard). The symptom was immediate (thinking back about the course of events) I no longer had backlight also FAN didn't kick in again.

I do not have the original BIOS from the board (i7-16GB, old board was I5-8GB). I only took a backup after this happened. I bought a quick subscription on another website and I tried to flash a clean ME bios. Still no backlight. I ordered a new EC (I do not have a programmer capable of flashing it atm, should come soon from Ali). The EC is IT8225VG-128 (128 BGA ITA). I replaced the EC and reflashed the clean ME BIOS. The issue still persists.

More info:
All power supplied working except VCCGT (but this is expected I think since it is bring up only after POST). VCCGT measures around 1.4Ohm to GND. I have VCCCORE x2, 5v, 3v3, 1v2 (DDR) and 0.8V. Charging the battery works. Laptop runs off wall socket and battery.

I have a thermal camera and SOC seems fine. Heats up good and is uniform (no heat spots).

When laptop powers the power led (white) goes on. Problem is charging light switches to white and starts blinking 4x white then pause then 4x white then pause while power led stays solid white. No signal on HDMI. Keyboard works (Caps lock on/off).

All power good signals are checked and ok. Idk if EC really needs programming for internal TCM or it can bootstrap from SPI (Bios) with ME cleared. Maybe you have more experience since I rarely have time to repair electronics lately.

Boardview is on the website. The issue is that L_VDDEN_PCH and LCD_BACKEN_PCH is not going HIGH on the board.

Would really appreciate if you can give some help.

Best regards,
ND

LE: I think most likely BIOS/EC issue. Fan spins when CPU hits around 80 degrees. This means that EC works to some extent no? I think FAN is controlled by EC.

[mcplslg123]

Yes, fan is controlled by EC and too me its seems new EC has indeed self programmed else you wont get kbd numlock key on/off on toggle. In short,the mb is posting correctly.
On some boards HDMI dont work in dos mode and works only in windows. So best bet is to replace the edp cable first and then troubleshoot further.

[Sephir0th]

Agree and I'd call this bad luck otherwise, since the most likely reason for the actual problem would be that something happened with the PCH. If PLT_RST# is indeed deasserted then you should concentrate on L_VDDEN_PCH after cable replacement.

[nd03]

Thank you very much for the answers mcplslg123 and Sephir0th. Much respect.

Would like to understand a little bit more. Maybe you have more experience on those matters. In my entire works on electronics (quite some devices and years) I have never seen something actually killed by ESD. The reason is that all devices has quite strong ESD protection in the pads when they die is bonded the the actual capsule.

Wouldn't it be a good try to actually install windows on an SSD with MBR/Rufus on an USB and try to boot off that? In theory I should get HDMI working? (maybe my thinking is wrong).

Couldn't this still be an EC issue? or is it out of question if this thing posts?

I am too thinking maybe PCH could be fried somehow but I really find it unlikely. If that is the case I can replace the entire SOC np but I know no reputable vendor that sells those. Do you know anyone selling good SOCs?

Cable replacement (or maybe something happened with the controller on LCD on the actual ESD discharge) would be extremely hard since it's not exposed when I take out the plastic cover. It's one of those rotating touch screen stuff seems the entire frame is glued and the actual control board is under that.

EDIT: Also it seems that VCCGT rail is at 0V but I do have PWM 1.4V on DRMOS. I don't exactly understand how this can happen is PWM is present I should have 0.8V if I have PWM. Could be that both iGPU and PCH are toast.

[nd03]

I bought a new screen assembly (still in transit). I broke the last one taking it out. Also my RT809H programmer arrived. Tried to connect it to IT8225 via 32P ITE extension board however it's not getting recognized. Do any of you have experience with RT809H and ITE programming? I mapped pins myself according to boardview in the software.

[nd03]

Seems I did not fry the SOC. New screen works but china hits again. the EDP is not fully good. artifacts when I move it. Ordered new. Seems original IT was fried. I only have an issue left with this board. No HDMI signal in windows. Can you give some guidelines please? What should I check?

[nd03]

Hello guys. Thanks again for help. Just an update. Second display was fixed by changing LVDS connector. Laptop had an issue with touchpad as well but I wired it directly. HDMI was the HDMI repeater (parade) and a bad switch (N Channel MOS 2N7002 that was switching the 5V to HDMI +5VSHDMI I had 1.2V after changing repeater instead of 5V).