Microsoft surface laptop 4 1951 turns on for 10s. Missing 1P8VSB_EN

[sofles]

Hello

I have Microsoft surface laptop 4, model number 1951. I bought it broken and I'm trying to fix it for myself.

Long story short, I bought it as dead. No voltage on battery, not turning on. I replaced battery and PD controller TPS65993AD and now Surface charges battery and turns on.
The problem is that it shows microsoft logo for 10s and then turns off.

I checked power rails and I'm missing 1P8VSB_EN power rail, it is not turning on because it has missing SLP_SUS

And there is my question, is that more likely related to hardware issue or BIOS? I tried to clear BIOS but I have got only CH341 programmer and I have error during programming BIOS and I'm not sure if this programmer supports Winbond 25R256 ICs?

Thanks for any help

[mon2]

What is the voltage to ground of VSUS_ON? Voltage to ground of EC_RST#?

[sofles]

Thanks for answer
VSUS_ON has 1.8V
I could not find EC_RST# in schemes qand I'm not sure where to measure

I found reset signals like
DEVICE_RST# has 3V
SAM_RESET# has 1.8V

[sofles]

I have completely deslodered BIOS IC and try to run surface to check what will happen and no change, it still shows microsoft surface logo for 10s and shuts down. That makes me wonder is there possibility that SLP_SUS may be programmed in BIOS?

SUSACK# and SUSWARN# have same voltage 1.67V
RSMRST# before pressing power button has 0.4V and after pressing PB goes to 0V

[sofles]

Little update. I bought EZP2023+ with 1.8V adapter to program BIOS IC and same thing. It looks like I can't fully erase BIOS IC, when I erase IC and then read its content it still has some data. When I write to IC I get error on verification. I'm not sure what is happening

[mon2]

Is the target flash chip removed off the logic board or using the large clamps? Suggest to remove the flash chip off the board so the IC is isolated from other circuits.

Does this programming tool support exactly this target flash IC part number?

[sofles]

Is the target flash chip removed off the logic board or using the large clamps? Suggest to remove the flash chip off the board so the IC is isolated from other circuits.

Does this programming tool support exactly this target flash IC part number?

Yes it is removed from MB.

BIOS IC is Winbond 25R256 but it is auto detected in programmer as 25Q256FW 1.8V. Programmer software doesn't have 25R256 in database, I could add one but I'm not sure all parameters.
With 25Q256FW selected I can read whole IC, if I want to erase it most of IC is FF but there is still data left, I can write bin file but it gives me an error while veryfiying

[mon2]

Interesting reading:

ezp2023 doesn't erase all of chip - Badcaps

[sofles]

Interesting reading:

ezp2023 doesn't erase all of chip - Badcaps

Thank you for help, I read this but no change. I used now CH341A as they said that it is more realiable but after erasing IC I still have data on it (attachment 1), I cant program anything with CHA341 as it freezes on programming IC. When I thry to program with ezp I get error on 1h (attachment 2)

[mon2]

Change the speed setting to the slowest speed and then attempt the full chip erase again.

[sofles]

Change the speed setting to the slowest speed and then attempt the full chip erase again.

Same thing, it took almost an hour to erase and write IC but as soon as it gets to veryfying it shows error 1h