• Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0

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#1 Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


by Mobotool 29 September 2025, 16:03
Hi to all, this laptop came with no signs of life, no battery chargin and no start.
I found that the main 19v rail was almost shorted, it measured around 7 Ohms , then searching better I found a shorted MP86941 DrMOS (between Drain and Source) that converts the 19 volts into the PCH core voltage...
I was going to chuck the towel, but I had a new same DrMOS then decided to solder it in, then I connected the power jack and the system now powers almost on, all the voltages rise but the CPU core and VGFX core.
Externally I only see that keyboard backlight lights up for 2 seconds, FN and Capslock leds light and stay up forever, and that power led (near power jack) starts blinking continuously after 4 seconds.
I know that 19v may have hit the PCH core then it should be definetly damaged, but I can't explain why RAM voltage (and others like 0.9v) rises but CPU core doesn't.
I don't have any Intel 10th gen power sequence, so I don't know if RAM voltage should rise before or after CPU core voltage.
Theoretically, PCH should output SLP_S5 and SLP_S4 signals if it works and all previous conditions are met, and then after RAM voltage should rise, so in theory PCH maybe still work...maybe only on some degree...

I've inserted a Clean ME bios image but nothing changed.

I've already searched for info and problems about similar Huawei laptops that uses the same Monolithic Power circuitry with the MP2979A IC, and it seems that many users had similar problems with this IC (Fn+Capslock leds on indefinetely), that has an integrated eeprom that may corrupt and it's difficult to restore without the proper development tools.

Please, anyone could share a schematic or a power sequence from another HP latop that uses a similar 10th gen Intel CPU?
Or maybe suggest other things to try?
Thanks

Edit: I corrected the code of the shorted mosfet, it is MP86941A

Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


by Google Adsense [BOT] 29 September 2025, 16:03

#2 Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


by Vogelek23 29 September 2025, 19:12
Mobotool wrote:I found a shorted MP86941 DrMOS
Please post a photo with that faulty DrMOS position highlighted.

Mobotool wrote:I don't know if RAM voltage should rise before or after CPU core voltage
Always after. The CPU core voltage is produced at the end, when all other voltages are present and all their Power Good signals are high (ALL_SYS_PWRGD signal goes then high and turns the CPU core supply on).

#3 Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


by Mobotool 29 September 2025, 19:53
Thank you master for the quick answer, and for the tip about the power sequence :)

Here is the photo of the (once) shorted DrMOS
Image

#4 Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


by Vogelek23 29 September 2025, 20:05
What is the current resistance to ground at the "R47" coil next to this DrMOS?

#5 Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


by Mobotool 29 September 2025, 21:08
I measure 6.5 Ohm.
I know, it maybe a bit low to be a PCH core static resistance...but I can't explain why other voltages rise and not the CPU one.
Since I have no schematic nor boardview of this mainboard, I don't know where to measure other typical power sequence signals to better understand how things are going

#6 Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0  [SOLVED]


by Vogelek23 29 September 2025, 21:16
What is the voltage to ground on this coil when you turn the MLB on?

EDIT: The PCH part of this APU is faulty for sure. 10th generation CPU should have ~40-70Ω at +1.05V power rails.

#7 Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


by Mobotool 29 September 2025, 22:06
I measure 1.05v on that coil when MLB is turned on.
I suspected that the PCH could be damaged since I measured the same resistance on the +19v main voltage rail when I took the first measures, and it was the same as the PCH one ... in Japan they call it harakiri, ouch :(

Re: Huawei Matebook D14 - NbB-WAH9Q - Shorted DrMOS MP8694 - DAH98NMB8B0


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