Document from ICOM about the battery replacement with the procedure to save memory contents.
RAM Card Backup Battery Replacement Instructions
Procedure to re-program the IC-751 or IC-745 RAM board
IC-751 HEX file (does NOT work with 745, despite VU2SBJ comments)
R-71 HEX file with extended frequency range (N2CBU format)
IC-745 HEX file (N2CBU format)
IC-745 BIN file (N2CBU format)
IC-271 BIN file (RW3XA format)
IC-751 BIN file (RW3XA format)
IC-761 BIN file (RW3XA format)
Includes the schematics to build the programmer. This is the one I have used with success.
RAM Module Programming Utility (N2CBU)
Includes the schematics to build the programmer (different than the N2CBU one)
RAM Module Programming Utility (RW3XA)
If you have any BINary or HEX files for other Icom rigs, please, share them with me and I will add them here. Thanks!