I bought an HP LaserJet 4050N printer from Craigslist for really cheap. The guy who sold it said the only thing wrong with it was the network card, but now that I've been trying it out, I'm not so sure that was the only thing wrong. I confirmed that there was some kind of problem with the network card; I'd plug it into my router but the green light would not activate. So I purchased an HP JetDirect 600N network card off eBay, also for very cheap.
I swapped out the network card, and that appeared to work. The green light turned on when connected to the network, and my computer could see the printer on the network.
However... as soon as I try to print to the printer over the network, it immediately pops up a message on the printer's display that says error # 79.8109. I'm not sure what that means.
So I tried next to connect to it directly using the parallel port. I don't have a direct parallel cable; instead it's a parallel-to-USB cable which I'm using on my Windows 8.1 (x64) machine. That seemed slightly more successful, but still not great. When I tell it to print a single test page over that port, it continually spits out page after page. In the midst of doing this, it may or may not show "41.5 Printer Error" on the display (while continuing to print anyway). Every other page is blank, while the remaining ones have one or two lines of gibberish on top (pictured). Then it inevitably paper jams after a dozen or so pages. I'm using the HP Universal Print Driver for Windows PCL6.
I also noticed there's a small bit of rust on the back panel.
I realize this is a bit of a longshot, but I'm still asking here anyway with the hope that someone might have more insight on these old printers. I know that when they do work, they work really well.