...of ships and sails and sealing wax, of cabbages and kings... *smacks own head with printer* Owww... sorry.

*ahem*

@Miklós Márton suggested that the ROM might be able to be read but not written to, and that I should try to erase and reprogram it.

I just now fired up the programmer, wrote the chip full of FF's, and then rewrote the original programming back. Both attempts were successful, meaning that the ROM itself is likely not the source of the issue.

While I have not discounted the possibility that the issue is rather the printer, and not the printhead itself (the flippin thing works fine when it wants to... namely if I douse it in tremendous quantities of 91% isopropyl... I get about half an 11x17 page that way and then, well, green-orange-orange-orange-orange-orange) -- I am prioritizing investigating the printhead, because it's by a very considerable margin more easy and simple than disassembly and troubleshooting and subsequent reassembly of the printer proper.

Setting aside the issue of, this printer is juuuuuuust new enough that it is designed /not/ to be disassembled... my mother's house is the victim of some rather gnarly actions by a combination of nature, economics, and the homeowner's insurance company, and thus she is in the middle, more or less, of having repairs done to clean things up. While I absolutely WILL NOT get into any degree of detail on this, suffice to say that the relevant printer, not being one she typically uses, is in a room upstairs that the repair company is using as something of a closet while they otherwise put things back together as best they can. While the room itself is navigable to some extent, and the printer is reasonably accessible, it is not a situation where I can reasonably move the printer around or otherwise access all sides of it, and as such, any attempts to access its innards would be something of a Herculean task.

Further, that part of the house (the upstairs) has never had proper heating or cooling -- we usually use a weird, complex scheme of window and box fans and cardboard baffles in summer and there are baseboard heaters in most of the rooms up there for winter. It sucks but it's reasonably manageable once you're used to it, and it's approximately functional enough to make the floor habitable for most of the year. The reason for this is, again, money. The house was originally a single floor... my father and a local family who were friends, added the second floor on after my parents bought the place. This was in the early 1980s, and air conditioning was (oddly enough) kind of a new thing back then. A unit was installed, but it by no means had the horsepower to loft air that far up, and so ducting was never run. While the original air conditioner has long since been replaced, a fairly consistent money issue has meant that that floor of the house has, sadly, never been given the climate control it properly deserved.

That said, this Saturday, the local weather reports indicate, is when Fall is supposed to properly arrive, at least in terms of temperatures. Depending on exactly how that plays out, along with my energy levels, I may take up the effort, or at least make the attempt to do so, required to make the printer properly accessible for a partial teardown. There's a lot of rearranging that has to happen in that room, for that, but we'll see... don't hold your breath, though.