Last night was dedicated to screen changing, and now I found some time to test the procedure.
The problem with modified boot.bin and rgn_tool was that I'm using ver.078 and you are using 084.
So, as per instructions copied rrgn41.... to update.txt. No ldr.bin on SD. Puted SD card in the unit.
From modified 0827064boot.bin created rgn file. Using updater.exe entered preboot mode, load 08271000640.rgn, and updater said success.
The unit's screen stayed at Loader Loading (Garmin).
Turned off the unit and checked did I have file 41_backup.bin. The file was not generated so I have to assume that chip is dead.
@ Neil
Just as a last resort - would you be so kind to prepare for me 08271000640.rgn in case I did not changed correct string or something else I did wrong?