Greeting Fritters.I recently (like day before yesterday) acquired an Apple SilenType printer - complete with interface card and a roll of unopened New Stock Apple Branded paper.Well, I seem to have a bad pixel and the stepper motor isn't advancing the paper. I have a part for the stepper motor coming. Hopefully that will solve the latter issue.
Any ideas on how to repair those two issues?
It's a thermal printer. I've never taken one apart so I am not sure how it works internally, but you might be able to see if there is something visibly wrong with that row in the heating element in the print head. Also check for an electrical connection issue. Unfortunately I think it may be a difficult problem to diagnose. I'd start with a careful cleaning and inspection though.
The Silentype is pretty easy to disassemble, just be real careful with the string that pulls the printhead side-to-side. I wouldn't want to have to figure out how to restring it and get the tension right.
I had a similar "dead pixel" problem with mine and managed to clear it up by gently dragging a piece of card stock (which is much thicker than thermal paper) across the paper side of the printhead. I then ran the SilenType demo program which results in a fairly long print-out.
As I recall, there is a flex cable that connects the printhead to the PC board. Make sure it is securely connected and perpendicular to the connectors.
If neither of those things fixes it, you may have a bad heating element in the printhead or a bad ULN2003 driver chip (on the board inside the silentype.)
https://www.applefritter.com/files/2026/04/09/Apple%20Deserializer%20Driver%20Printer%20-%20Schematics%20050-0023-01_0.pdf
I added a diagram, it should help
A user in a Facebook group pointed me to the following videos:
https://youtu.be/afF4VvgyeiU?
https://youtu.be/iF4keC9i2x0?
https://youtu.be/LBTimqABhKs?
https://youtu.be/G5u7mO0-yzs?
https://youtu.be/ki-AuIBJi7c?
These have been a great help. I was able to figure out how to replace the ribbon and head on my own - without breaking anything, found out that the pulley string isn't that hard to replace, and that there is a diagnostics tool for head alignment (though no real instructions on what to do with "fails").
Separately, I've discovered that there is a pretty bad warp in my top cover that doesn't appear to be interfereing with anything but apparently is displacing the platen enough that whenever the lid is in place (doesn't even have to be screwed in) the print quality fades almost completely.
Going to try to restore the lid, but that's risky. May need to install standoffs or something, but that could interfere with the metal lid.
UGH!
Thank you for the research and links to the videos! The pulley string on mine is badly frayed and really needs to be replaced. Fortunately this doesn't look too difficult once you see it done. I'm just wondering what kind of string is a suitable replacement 40+ years after the original design.
The youtube videos show that it's a hollow braided type of string. That is, if you were to take the string out and hold a piece between your two hands and sort of press it together it would have an inner annulus like a "chinese finger trap".
I would conjecture, therefore that a similar type of cord would work in its place. Measuring it would need to be done, but you can get 1mm braided nylon cord in spools on Amazon.
The type, maybe that is used in venetian blinds? link to venetian blind cord
Or perhaps something like Marlow Excel Pro (leisure marine) rope which you can buy in small spools. The smallest they make is 2mm, but if you strip the outer cover from the braided inner core, you can probably get to 1mm and use that. link to Marlow Ropes Excel Pro
Or even paracord. They make very small diameter, extremely strong no-stretch lines you can buy in small spools.
Amazon link to 3/64" paracord