Hi [USER="613891"]ymongo[/USER]
Glad to hear that my solution also helped You. There is something wrong with latest bios from HP (do they want to brick old devices?).
About U68 my dump wouldn't help you since this is specific data (serial number etc.). As I wrote in case of no other solution you can clear U68 flash main bios U19 and it will show post again, do it if others solution fails.

Best regards
Lukaszymongo...

Hi,
I've managed to fix my pc.
There was no issue with hardware but rather latest bios version R26 02.21.01 Rev.A, it is going to some weird state with black screen after update.
I found some older versions of bios for my elitedesk 705 g5 mini R26_021100 (just select old WIN10 on hp site and it will show all bios versions).
I have trimmed start bytes and leave only last 16MB (using HxD) and flashed this to U19 Windbond chip and then my pc returned to life.
Later on using USB drive I have updated to 02.20.00 Rev.A (one before latest bios) and it still works.
...

Do You know what is inside U68? What kind of firmware information, maybe this is corrupted?...

Serial 8CC0230DB5
Product number 6AU06AV
​

Hi,
With old u68 dump and latest bios (the one which I was updating from windows and all troubles started)
R26 bios extracted from hp package.
After flashing bios (u19) PC restarts few times and boots to windows, but after restart it goes to original black screen, fan spinning, no keyboard response.
If I reflash U19 then process can be repeated, I can enter to bios setup, boot into windows but after windows restart I get blank screen
I removed hard drive with windows and reflashed u19 and got this message (attached picture) and the it goes to usual blank screen....

I have small progress.
Before any modifications I also dumped U68.
I see that now U68 has different content, so I reflashed it with my original backup and now error signal is gone but there is still black screen.
Do You know what is inside U68 ? As I understand bios is in U19 am I correct?
Here is original U68 backup...

Hi,
Thank You for uploading a bios file.
Unfortunatelly I still get 6 red and 3 white from the beginnig. I've disconnected ram there is the same 6 red and 3 white signals.
If I even clear bios chip the I get the same behavior
May it be permamently bricked? I was trying to remove battery it didn't help either.
Is it possible that maybe cpu is damaged ? (it was working before bios failure)

Regards
Lukasz

Hi I have issue with my hp 705 g5 mini 3400GE

I was trying to update to latest bios HP BIOS and System Firmware (R26), but after update screen and few restarts screen got blank.
No keyboard reaction.
Here is bios dump (16MB winbond) neoprogrammer, ch340

Unfortunatelly I've tried one of the above attached bios files and now I get 6 long red and 3 white signals.
Do You know what that mean? Is there any help for my board.

Serial 8CC0230DB5
Product number 6AU06AV

Thanks for any help....

Hi everyone,
I'm embedded software developer. I have some experience in fixing stuff. I found this forum trying to fix my hp elitedesk g5 I hope I find some help here.

Best regards.
Lukasz