Error codes under SM do have to be considered alongside when SM appears as well as that it appears, so you could be on the money with an alternative. The rudimentary POST of an SE has long since passed by the time of raster-arrival, and the immediate descent into the abyss after raster, which should have been followed by mouse-tracking, Happy Mac, splash screen and so on argues a software failure. Hence the illegal instruction error, perhaps, because whatever the system was reading was incomprehensible to it. However, the only software in your SE sounds to be firmware, busy driving Start Manager. If your firmware is bung, it suggests that your ROM is bung too, and another candidate for the large cleanup broom.

Your way may be long and convoluted. Best of luck, nonetheless, and you will enjoy it when you conquer.

de