Help with damaged bootloader in EB600

[toptnc]

Hello

I have a Inves Ebook 600 (Netronix EB600)

It seems to be bricked because all you can see is a garbled screen, but the device reacts to buttons. I can power on and power off. I can see how the screen change with more garbled contents. I can launch a firmware upgrade, and it seems to terminate ok. And i cant mount it with USB cable.

Firmwares I have tested
bq 1.0, bq 2.1, bq 2.3
cool-er 206 (from here https://www.mobileread.com/forums/sho...7&postcount=15)
Original Inves Firmware.

I have modified upgrade script to generate a log, and it seems to work ok, so i don't think that the ebook is bricked. It seems like something in the bootloader breaks the graphics and everithing looks garbled after that.

I have searched for bootloader repair methods, but all I have found is a post in russian explaining how to make a serial cable (and solder into motherboard) to debrick the device.

Since my device can run a SD upgrade, ¿is there any method to flash a bootloader from a SD card?