I kept the 'Help' button continuously pressed, from the powered off state until 'Utility' starts to flash, like I wrote in my update log.
-DG4000Update.GEL should be copied alone on the clean formatted USB drive (mine was FAT32)
-To update FW
- insert USB with desired GEL file
- power down the DG4102
- keep the 'Help' button pressed while pressing the 'Power ON' button
- release the 'Help' button when 'Utility' button starts to flash
- from there, leave the unit running, the buttons will start to blink one by one, starting with 'Ramp'
- after about 10 minutes, the DG4000 will restart itself, firmware update is now done
-To see FW version press 'Utility' -> 'System' -> 'System Info'
-To see detailed version press 'Utility' -> 'System' -> 'System Info' -> 'G1' ->'G3' -> 'G5'
where G1...G5 are the grey buttons on the right of the screen