Found some stuff at the scrapyard

It's mildly easier to use with a normal PC than the -B model (HPIL, battery powered). Interestingly the -A version has an HPIB-HPIL interface feeding HPIL to the main board (the interface is a modified (different firmware) version of the HP82169 IIRC. Interesting #2, the custom HP controller chip in these printers has a built-in ROM with the control firmware, but external font ROM and RAM. These communicate over what is essentially the Saturn bus, as found in the HP71, etc. I read somewhere that the official reason for 'THINKJET' was 'THermal INKJET'. I suspect that is very much a backronym. It is a thermal inkjet printer, the cartridge has little heating elements that boil the ink and cause a drop to be squirted out. A couple of words of warning about those cartridges. Firstly the ink, at least in older ones, is ethylene glycol based. It's toxic and attractive in taste to some animals. Keep those catridges away from cats, dogs, etc. The ink is also corrosive. It can corrode the metal faceplate on the cartridge, then drip onto the flexible PCB that connects the cartridge to the rest of the printer and corrode that too. If you ever have a Thinkjet with missing dots, that's what has happend (at least 99% of the time). The only source for replacement PCBs now is other Thinkjets. So don't leave the cartridge in the printer if you are not using it. Incidentally, if the 9153 is the drive unit I think it is, it has a very odd HP-interface hard disk in it. There is one ribbon cable (40 wires I think) carrying power, control signals and raw data. I seem to remember the head positioner is a stepper motor, but it does micro-stepping as part of the design. -tony