Notch another win for the 'propes...
I decided to try and use my Canon PJ-1080A again after a while (known as the Canon Ink Jet Printer to the Office System), and while I was able to print C, Y, and K, I wasn't getting any magenta out of it. Repeated efforts with the pumping mechanism as described in
the manual (including the "wait for six hours and try again" advice) weren't working.
The PJ-1080A brings the troubleshooter the triple pleasure of considering electrical, mechanical, or hydraulic faults. After poking around with an oscilloscope I was pretty confident my problem wasn't electrical (side note: it looks like each time one of the print heads squirts out an ink droplet, it's getting goosed by a -50V pulse from the control board). I couldn't easily investigate whether the thermal squirter mechanism was still functional (it's very difficult to access), so instead I decided to "search for the keys under the lamppost" and try and fix a clog.
This photo may help with the following:
https://photos.app.goo.gl/4Bz46mg7qaAcYh139so might this page of the manual:
https://archive.org/details/CanonPJ1080a/page/n9/mode/2upMy strategy was to try and dissolve any dried ink around the print heads with isopropanol, or as I like to call it sometimes, "the 'propes". I couldn't easily remove the head carriage, so I gently pressed saturated, folded strips of laboratory tissue against the heads, which look fairly fragile. It was necessary to unscrew the cap-and-pump assembly (in the photo, see the green lever and the white, plastic cap with the "761785" label) so I could lift it out of the way for better access to the heads. Once I'd blotted away about as much ink as it seemed possible to remove, I tried again and happily we were in business.
"Nobody collects printers..."
