Yes 4C 28 F1 4C 3C D4 are correct. Oh, ADTPro over audio, I haven't done that, just with the serial card. Volume settings are touchy when it comes to audio transfers.
You do really need to get an AppleCillin diagnostics disk for the next step. I bet it will boot.
You do really need to get an AppleCillin diagnostics disk for the next step. I bet it will boot.