Thank you for the dump but it seems to be incomplete, it's half the size (32Kb) of the two other copy I have (64Kb each), tried it anyway (for the little time it takes) and with it the board doesn't work (no video output, not recognized by tuttletech in any way), maybe you read the eprom as a 27c256 insted of the (supposedly) correct 27c512 ? can you check it ?
No problem sharing my copy of the rom for the card, here's the two version I have, 1.15 was the original version on my card and 1.161 is the one found on the bitsavers.org archive, this two rom works without problem at least with my revision of the Thunder/24.
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Thanks for your time !