I would like to help out here.
First of all its important to know, what MCU (controller chip) is used on your Minimig board.
Is it the original PIC chip or the ARM controller?
PIC is a slim TTL-looking chip fitting the slim socket between SD-card slot and the MENU button.
ARM controller is an additional pcb (board) covering the SD-card slot with an micro-USB port at its left side.
After knowing this, there are 2 ways to get you Minimig back to work:
1. finding out the current Firmware release working in PIC or ARM chip and than using matching FPGA core (Minimig1.bin file) version.
2. Updating the PIC or ARM to its current release.
Fashing PIC is a bit hard because it only can be done via RS232 (serial) connection to a PC or real Amiga.
Flashing ARM will be easy if the Minimig is showing a Kickstart screen. Otherwise the ARM need an USB update with a special Atmel tool called SAM-BA or SAM-PROG running in Windows or Linux.
If you can remember any feature of the OSD menu when Minimig was running, it could be helpful finding the right FPGA core version.
You also could try out some releases until the matching version is found.
FPGA cores are stored here for download:
https://code.google.com/p/minimig/downloads/listEverything named
Fxxxxx (F = FPGA) or full binary release can be used.
Just try all the available Minimig1.bin files in the archives, at least one will work right.
After the board is working again, an update to current release 100818 for PIC and ARM and also at least for the FPGA is recommend.
To enjoy most compatibility and features the current FPGA release
FSB131020 will be right.
If there is any question left, I will try to help on.
Maybe the
http://www.minimig.net forum will be better/faster since I am online almost every day there (known as boing4000).