I must add my name to the list... I own a SDG805 since many years (out of warranty); today I tried to update the firmware from SDG800_V100R008B01D01P08 (which worked) to the last version, SDG800_V1.08.01.15R2. Even though I followed the instructions to the letter, the machine went into bootloop when it automatically restarted at the end of the update. It is now locked at the "Siglent" splash screen. May I have the recovery image to put in the USB key? If necessary I can also open and tamper with the circuits (but I'd rather not). I'm sending a PM with my e-mail to tautech, just in case... Thanks in advance!
Your version was really very old V100R008B01D01P
08As you can see it is not included even version history pdf (included inside update zip)
If I remember right it can not update directly from this extremely old version. It may need first intermediate update.
(sad there is not list of compatible FW versions list, but when user see his current FW is not even listed in new version update package "version history" it is good signal to user that first is good to ask before update... )
But now it is late for this because its status is now as you told...
I am quite sure, after this failure, it need now SD card recovery. For this there need do also some simple SMD rework (before SD recovery and then return changes back to original. Enough bad mistakes there and it is electronics recycling stuff. But when all is done carefully ok, it is quite robust way to Recover. There is instructions in recovery package including also Hewlett-Packard tool for do SD card formatting.)