HP Pavilion 15-eh Board DAG7HAMB8F0 - CPU throttling to 0.4GHz (PROCHOT_EXT) and black screen

[m1ch43lzm]

Hi, this is my personal laptop, which the original board (lets call it Board A) blew up PU8700 (TPS51486), making a hole on the board, i had left the laptop at my desk one day with the battery fully charged and didn't touch it for a week, but when i tried to turn it on it didn't
Thought the battery was dead, so i plugged in the charger then tried to power on, the power LED blinked once, charged LED still orange, unplugged the charger, plugged in again and I noticed the "magic smoke" smell, so i unplugged the charger, removed the back cover and saw the blown IC (the "magic smoke" escaped from it) next to the RAM slots, and when I removed the blown TPS51486, it left a crater on the board with burnt PCB
Similar issue as this thread: https://www.badcaps.net/forum/troubl...on-15-eh1815nd
I tried to rebuild the crater but I gave up, I even ordered some TPS51486 ICs from aliexpress
Anyways, bought another board from Aliexpress, and this "new" board has some issues, let's call it Board B

On battery:
- The board appears to work fine, it boots normally to Windows, but sometimes the CPU would throttle to 0.4GHz depending on load, checking with HWINFO64 reveals that Thermal Throttling (PROCHOT_EXT) and Thermal Throttling (HTC) report a value of "Yes" when that happens
- Running CPU stress tests (Cinebench R23), it would "thermal throttle" within 30-40 seconds, the CPU temp doesn' get hot enough (max 70 deg. C and the fan woudn't even turn on), and stopping the stress test and it takes around 2 minutes for PROCHOT_EXT to get "no" as a value, something has to "cool down"

With charger plugged in (doesn't matter if the battery is installed or not)
- Same thing, boots to Windows (I'm writing this right now from this laptop), but running Cinebench, the screen would go black almost instantly and the power LED stays on, holding the power button works to turn off the laptop, and can start again
- Measured VCC_CORE and VDDCR_SOC when the screen goes black = 0v
- Black screen can also happen when watching YouTube but it takes some time, sometimes just "thermal throttling" with the CPU stuck at 0.4GHz for some minutes, simple usage like web browsing doesn't seem to trigger the fault, as i'm still typing this post
- Battery does charge normally

I don't have a thermal camera

CPU VRM controller on this board is uP9531P, but it's on the back of the board, no way to easily test with running system as the board is assembled in the laptop (and power button is on the keyboard), the schematics state RT3662AMGQW, maybe they're pin compatible, i only have RT3662AC from Ali (maybe legit, maybe fake, who knows)
CPU MOSFETs are AOE6936
SOC MOSFET is AONY36356

I don't know what could trigger PROCHOT_EXT when on battery and/or disable VCC_CORE and VDDCR_SOC when under a CPU stress test with the charger plugged in, yet the test would start but "thermal throttle" when working on battery only

CPU temperatures on this board B don't go high enough to "normally" trigger thermal throtting, the max temp I see is 67-70 deg.C, on the original board A, CPU could go 90 deg. C and not thermal throttle under any circumstance

Original board (Board A) has CPU: Ryzen 7 4700u (model in BIOS: 15-eh0xxx)
Replacement board (Board B) cPU: Ryzen 7 5700u (model in BIOS: 15-eh1xxx), same board number DAG7HAMB8F0
There was almost no price difference so i thought i would get a CPU upgrade at the same time😂

Board A
BIOS version (last I remember) was F.29
EC version: 80 something, i don't remember, board is dead
Board type: 87C5 (IIRC)

Board B
BIOS version: F.25
EC Version: 78.51
Board type: 88D0
The solder joints at the BIOS don't look factory soldered (and that seller on Ali placed a "warranty sticker" over the BIOS), likely the BIOS IC was removed for programming whatever it has right now

Any suggestions about fixing this board? I have Board A as a donor (or should I try to fix board A?)

Schematics/boardview: https://www.badcaps.net/forum/troubl...=2#post1810731
Attached pictore shows PROCHOT_EXT and HTC change to "yes" on HWINFO64

[m1ch43lzm]

Pictures of the damage on board A (original board from the laptop), if anyone is interested, I already cleaned the soot, second picture is the "before" state

Also the 2823D IC on the left from the first picture was shorted

[mon2]

Not sure but PROCHOT_EXT may be an open-drain pin so a pull-up resistor on this line is mandatory. Confirm it is present.

[m1ch43lzm]

mon2 according to schematics I can't find a pull-up on PROCHOT#
It only goes to 4 places
- APU itself, as APU_PROCHOT#, tied to H_PROCHOT#
- EC, H_PROCHOT#_EC, then goes through Q4702 and becomes H_PROCHOT#
- Charger ISL9238 PU8200, H_PROCHOT#
- CPU VRM controller PU8800 as VRHOT, which is tied together to H_PROCHOT# with trace jumpers R625 and R626

[mon2]

R622

[m1ch43lzm]

I must have missed it when looking at the schematics from my phone
Will check it later, when I get back to my other PC
thanks

[m1ch43lzm]

mon2 you're right, i took measurements from the Board A (dead), and Board B (the one i got from ali), i wont be able to replace the resistor right now, will update when i get time to do it properly
Thank you for pointing that out

Board A
R622 1.02k

Diode reading (red probe on GND) at R622 H_PROCHOT# 0.534

Thinking it was the thermistors, i took measurements anyway (yes, i know they're in parallel to other resistors in the schematic)

PR8864 15.9k
PR8816 15k

PR8823 15.08k
PR8852 16.52k

Board B

R622 440k-460k, varies every time i probe it, so yes, it's faulty

Diode PROCHOT# 0.440

PR8864 16.94k
PR8816 15.07k

PR8823 15.03k
PR8852 16.63k

R622 is a 0201 resistor near the heatsink, attached picture of the location

I added some notes about the location of a testpoint of APU-PROCHOT# and the trace jumpers R626 and R625 (they designed them to be difficult to cut on purpose, instead of just addind a narrow section to them)

So yes, heat in the area will probably make that resistor drift to a higher value, but i still can't find an explanation why it instantly loses VCORE and VDDSOC only when on AC power, while i start cinebench stress test
Have to try to replace it to check what happens next, whether i grab it from the donor Board A or find it in some other random board i have

[m1ch43lzm]

I'm back, replaced R622, PROCHOT doesn't trigger anymore when running Cinebench... on battery
Yes, it looks a bit misaligned as i used the soldering iron, didin't want to use hot air near the CPU, in the process managed to "lose" C602, placed it back with the soldering iron

But with the charger plugged in, if i start Cinebench, at the "Preparing render test" phase, laptop crashes with black screen, power LED still on (likely VCC_CORE/VDDCR_SOC goes missing again), on light CPU load it doesn't happen
The charger is 45W, original charger which came with the laptop

Noticed also that the fan wouldn't turn on at all unless i change the "Fan always on" setting on BIOS, the CPU temp went up to 90 deg. C while running stress tests and the fan woudn't turn on at all, could it be the EC firmware? Noticed that the soldering on the EC doesn't look factory

Something else is still wrong with this board

[m1ch43lzm]

Noticed something else, my keyboard (Latin American Spanish) has a "><" key next to right Alt, but that "><" key currently works as a Right Ctrl, it's not the keyboard language setting in Windows, as all the symbols match, and that key worked before as it's printed on the keycap
I checked pictures of the keyboard online, and only the US English keyboard has a Right Ctrl key instead of "><" (or something else, on other languages), maybe some hidden BIOS setting? (feature byte/product id?)
The BIOS from this board (88D0) is different than from the dead board, even HP website lists different bios updates for the 15-eh0000 and 15-eh1000, so i can't directly flash it with the dump of the dead board (87C5)

My keyboard / US keyboard layout



To sum it up:

On battery only:
Laptop works fine even on stress tests or heavy usage, doesn't trigger PROCHOT anymore since i replaced R622
- Cinebench does complete without thermal throttling
- Unigine Heaven does run without issue

With charger plugged in:
Laptop works for light usage, i'm writing this post from it, but it crashes to a black screen when:
- Stress testing with Cinebench, instant crash after starting single core/multi core benchmark
- Unigine Heaven doesn't crash, but i made it crash once with black screen/audio stopped after about 3 seconds of rendering
- CPUID powerMAX doesn't crash (i only tested for 1 minute), either CPU and GPU tests
- Sometimes randomly crashes with black screen depending on load, or a current spike (?)
- When it crashes, doesn't respond to Caps Lock, the only way to get it working again is to hold the power button to turn off, then press the power button again

Any help is appreciated