HP Pavilion X360 14-ba253cl power cycles

[ReparaPC]

I have received and HP Laptop for repair becuase of no power. Initially, i measured the 5V Rail on the board with a direct short to ground, i discovered that PU4451 was faulty and causing the short. I have now replaced the component and 5V are present as well as LEDs after pressing the power button. After a couple of seconds, LEDs go off and turn on again, being the board stuck on an infinite loop were it never fully powers. After some measurements with the board powered on, 1V_CPU_CORE is not present. The resistance to ground on the rail is 4Ohms, which i think is normal for a VCORE rail.
After following the power up sequence, i've discovered that most signals are following a pattern of high and low voltage (for example, if a signal has a normal operating voltage of 3.3v, it will go from 0 to 3.3v as the board loops). All of the signals and voltages from VR_EN to PM_SLP_S4 are following this pattern. PM_PWRBTN# is sitting stable at 3.3V.

There are no available schematics for this specific board, but i've found a schematic from another laptop that is almost identical, being the revision used for a similar HP model.

[MOD EDIT] LINK to schematic --> https://www.badcaps.net/forum/troubl..._mb_mv-18742-1

[ReparaPC]

Update:

I have decided to re flash the BIOS. i used a CH341A, and after doing it, the machine powers on, fan spins but no video display. 1V_VCCSA is present and stable, but 1V_CPU_CORE is not, as well as 1V_VCCGT. I've measured the corresponding enable and PWM pins on the chips related to this rails. On the EN pins, they all get 4.94 volts (same as EN on VCCSA) and PWM voltage on both sit around 2.5V. I'm starting to think that PU4601 is faulty, as the PWM signal should be much lower, as is the case for VCCSA PWM voltage (around 0.24V).

Any help would be appreciated.

[mcplslg123]

VCC core will rise only when all preceeding rails are working and SOC is not shorted. So check whether you have 1.8V/2.5V rail working or not.
Bios flashed is known good and me cleaned?
I dont find CH341A reliable as it writes bios without error but the flashed chip dont work whereas flashing the same bios file with programmer like RT8209X or SVOD works.
What is the resistance to GND on vcore rial?

[ReparaPC]

VCC core will rise only when all preceeding rails are working and SOC is not shorted. So check whether you have 1.8V/2.5V rail working or not.
Bios flashed is known good and me cleaned?
I dont find CH341A reliable as it writes bios without error but the flashed chip dont work whereas flashing the same bios file with programmer like RT8209X or SVOD works.
What is the resistance to GND on vcore rial?

Looking through the schematic, 2.5V is generated at pin 2 on PU5101 (RAM IC), the voltage is present. I'm not sure what IC is responsible for the 1.8V rail, the schematic i'm using points to an IC not present in this board. Please let me know if there's somewhere i can measure the 1.8V rail.
I will post a link to the bios i used, but i don't have access to other bios programmers. The resistance to GND on VCORE rail is about 4 Ohms

Edit: I've measured ALL_SYS_PWRGOOD, and there are 3.3v present, as well as on VCORE_EN. Correct me if i'm wrong, but SYS_PWRGOOD being present means that all other voltage rails are working properly.

[mcplslg123]

The bios you linked is saved from a working computer-so that means the me region is tied to that specific board.So you need to clean the me region.
The best way to rule out bios issue is to download hp bios update file from hp website and then just double click on it.You will get an option "Copy". Just select this option and a couple of files will be saved on your pc.
Next open your original backup bios in hex editor like HXD and press ctrl+F and type $BID in the search box and press search all. Now you can see the bid number of your original bios. Now flash the bios downloaded from hp update with same bid.
The file from hp update is always clean me.

[ReparaPC]

The bios you linked is saved from a working computer-so that means the me region is tied to that specific board.So you need to clean the me region.
The best way to rule out bios issue is to download hp bios update file from hp website and then just double click on it.You will get an option "Copy". Just select this option and a couple of files will be saved on your pc.
Next open your original backup bios in hex editor like HXD and press ctrl+F and type $BID in the search box and press search all. Now you can see the bid number of your original bios. Now flash the bios downloaded from hp update with same bid.
The file from hp update is always clean me.

Understood. Thankfully, i did 2 backups of the original bios before flashing the new one. I will do what you suggest, hopefully, the machine will work.

[ReparaPC]

The bios you linked is saved from a working computer-so that means the me region is tied to that specific board.So you need to clean the me region.
The best way to rule out bios issue is to download hp bios update file from hp website and then just double click on it.You will get an option "Copy". Just select this option and a couple of files will be saved on your pc.
Next open your original backup bios in hex editor like HXD and press ctrl+F and type $BID in the search box and press search all. Now you can see the bid number of your original bios. Now flash the bios downloaded from hp update with same bid.
The file from hp update is always clean me.

it's been a while since i've worked on this machine. I have explored the contents of both the backups and a bios file downloaded directly from hp website, following the procedure you suggested. Both have the seman $BID (08567). I'll attach pictures of both the backup of the original bios, and the one downloaded from HP

[SMDFlea]

it's been a while since i've worked on this machine. I have explored the contents of both the backups and a bios file downloaded directly from hp website, following the procedure you suggested. Both have the seman $BID (08567). I'll attach pictures of both the backup of the original bios, and the one downloaded from HP

If you post your bios backup in that thread you linked to at post 4 someone will fix it for you and transfer the DMI (serial number,windows key etc) to the new bios

[ReparaPC]

If you post your bios backup in that thread you linked to at post 4 someone will fix it for you and transfer the DMI (serial number,windows key etc) to the new bios

sorry, i got lost. What thread should i use to post the backup? From where i downloaded the initial bios?

[mcplslg123]

The link given by you at post#4. Post your bios backup there.

[ReparaPC]

The link given by you at post#4. Post your bios backup there.

Already posted the bios backup with serial number on the thread.

[ReparaPC]

i've tried the bios posted by SMDFlea. Still no video and 3 long and 5 short led blinks on cap lock

[mcplslg123]

Consumption on dc supply
01.With ram stick
02.Without ram stick