HP EliteDesk 800 G4 35W DM Desktop Mini PC - not posting after BIOS reset attempt

[llek100]

Hello, sorry for the long post, I just wanted to include any details that might help.

A bit of backstory - I currently have 5 of these MiniPCs - I got them for very cheap from Ebay. All of these PCs are BIOS administrator password locked without their drives.
I also got a G3 large tower, that I could reset the password of fine just using a header and a button on the motherboard.
So I thought that I could do the same with the G4 MiniPCs, oh how wrong I was.
First of all, I stumbled upon a tutorial, that apparently showed a BIOS password reset procedure - where I basically removed a PSWD header on the motherboard, removed the CMOS battery and held down a yellow button on the MB and plugged in the power, I held down the button for three restarts.
Then I put the header back, put back the battery and turned on the system - and the BIOS should have been unlocked. This was not the case and I ended up with three bricked MiniPCs.
This is what they are doing now: https://drive.google.com/file/d/1YN-...ew?usp=sharing

I am uploading all the BIOSes, number 1,2,3 do not post at all - like in the video - and are BIOS administrator password locked. And number 4,5 do post fine, but only are BIOS administrator password locked.

Serial Numbers:
1. - 8CC8471NLV
2. - 8CC8471NL3
3. - 8CC8471NLF
4. - 8CC8471NLT
5. - 8CC8420TJ9

The BIOS files are here, since they exceed the filesize limit: https://drive.google.com/file/d/115V...ew?usp=sharing

Please let me know if I posted anything that should not be here, this is my first time using this forum .

Thank you!

[hoaca388]

Backup bios files ? ( Compress them with winrar or 7zip and post them here.)

[llek100]

Sorry, I did post them but through a Google Drive link in the post. Here they are in two zip files, numbered.
I did not realise the upload size limit is per file.

[llek100]

So an update, I managed to unlock the BIOS-4-5 using an HP unlock python script.
This is the one if someone wants to do the same: https://gist.github.com/schorschii/7...7b65ff22c27337
You also only need to read, unlock and flash the larger 16pin XU21 chip.

However, I am still unable to boot the PCs with the bricked BIOSes - those are 1, 2 and 3. If someone would be able to help somehow rebuild the BIOS or something.
I am not familiar with fixing possibly corrupter BIOSes.

[hoaca388]

So an update, I managed to unlock the BIOS-4-5 using an HP unlock python script.
This is the one if someone wants to do the same: https://gist.github.com/schorschii/7...7b65ff22c27337
You also only need to read, unlock and flash the larger 16pin XU21 chip.

However, I am still unable to boot the PCs with the bricked BIOSes - those are 1, 2 and 3. If someone would be able to help somehow rebuild the BIOS or something.
I am not familiar with fixing possibly corrupter BIOSes.

Fix error , unlock yet. Use Hp unloker or RC unlocker to solve the problem.

[llek100]

Thank you so, so much! Number 1 and 3 do work completely fine now!
Number 2 flashes 6 times red and 3 times white. I don't know if that's fixable. It is possible that the backup file for 2 was somehow corrupted or something, since it was the first one that I grabbed the backup from, and was the one I tested a MPM unlocked BIOS that was present on this website, but was deleted because it did not work.

[hoaca388]

Thank you so, so much! Number 1 and 3 do work completely fine now!
Number 2 flashes 6 times red and 3 times white. I don't know if that's fixable. It is possible that the backup file for 2 was somehow corrupted or something, since it was the first one that I grabbed the backup from, and was the one I tested a MPM unlocked BIOS that was present on this website, but was deleted because it did not work.

Try

[llek100]

Unfortunately still the same with 2.

[hoaca388]

Unfortunately still the same with 2.

Check hardware.

[llek100]

Hello, it now works! I had to erase the PRVROM, or the XU68 chip on the mother board, the system then recovered it! Now everything works!

Thank you very much for everything!

[hoaca388]

[llek100]

Please one more thing, the number 2 has started showing the "There is a problem with the HP Endpoint Security Controller on the unti.", I am attaching a photo as well.
I am also attaching current BIOS dump. I do not know if this is fixable, since I am missing the original XU68/PRVROM backup from this device.

Also if there is a way I could support your work, please let me know.
Thank you very much!

[hoaca388]

Please one more thing, the number 2 has started showing the "There is a problem with the HP Endpoint Security Controller on the unti.", I am attaching a photo as well.
I am also attaching current BIOS dump. I do not know if this is fixable, since I am missing the original XU68/PRVROM backup from this device.

Also if there is a way I could support your work, please let me know.
Thank you very much!

https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-laptops-tablets-and-mobile-devices/bios-requests-only/3305683-i-have-hp-probook-


https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-laptops-tablets-and-mobile-devices/bios-requests-only/3325398-hp-clean-vss2-dumps-fix-endpoint-security-error