Ok guys, I was having the same problem. My flashed my X3 with X3_3294. Everything would flash fine and the xbox would turn off by itself after the flash was over, but when i turned it on, it would just turn off by itself. I tried flashing it with X3_1943 bios. After that flash, when I turned it on, the xbox stayed on, but there was no video. I kept flashing the X3 with different X3 bios versions and I found that X3_2914 bios actually worked. When i flashed with X3_2914, i turned on the xbox, and the flubber screen would come up and then the "xecuter rox my box" came up.
It seems every bios after X3_2914 would end up turing the xbox off by itself, and every bios before X3_2914 would stay on, but with no video. X3_2914 is the only one that works. I knew it couldn't have been my soldering because I've modded other boxes in the past and they all worked fine (although they're still running X3_1943 cause i never wanted to update them). I think something is up with the bioses. Not the chips themselves, and not the installs
It seems every bios after X3_2914 would end up turing the xbox off by itself, and every bios before X3_2914 would stay on, but with no video. X3_2914 is the only one that works. I knew it couldn't have been my soldering because I've modded other boxes in the past and they all worked fine (although they're still running X3_1943 cause i never wanted to update them). I think something is up with the bioses. Not the chips themselves, and not the installs