OK, I have soldered 24 wires to the ribbon connector on the printhead. I want to avoid ruining my logic analyzer, so I tapped into all wires using a scope first to find the high voltage line that would destroy the logic analyzer’s input. So far, I have seen some weird noise on two pins, some digital data on three other pins at around 3.5V. No line carried more than 3.5V when testing. There must be a line though that supplies 18V or so for the heating elements.
I will try to create a repeatable test pattern for further testing. I also need to find my probes to avoid noise on the scope.