I got this as part of a package deal with some other things recently, and figured I’d detail my experience in messing with this printer and troubleshooting some issues with it. Buckle in and let’s get started!
When I got it, the printer was super clean, however it was evident there were at least 1-2 dead “dots” or lines in the print. For example, the horizontal bar in the capital letter A was missing.
First, I looked the printer over and generally it was fine; I did notice that the sheet metal/foil cover on the print head (and what a print head!) was partially peeled open, revealing an interesting look at a first-generation dot matrix print head. I’m assuming that the previous owner started working on this printer by opening the head.
First, I tried the basics by simply folding up a piece of paper, putting some ISO alcohol on it, and running it past the print head, incase there were any chunks of dirt or dried up ink. That didn’t seem to do much of anything, although some dirt and old ink did clean off of it.
Next I removed the 4 screws holding the print head on the carriage and removed the print head off the carriage. I cleaned it up a little bit better with alcohol, and ended up having to use my phone magnifier and later a jewelers’ loop to look at the printhead pins. It was obvious that at least one of the the missing dots was sitting well below the rest of the pins, almost to the point where you couldn’t see it.
Each “pin” is actually driven off of a solenoid on the rear of the print head; they literally look like tiny rocket boosters from a space ship. Each solenoid is threaded into the print head assembly, and then a jamb nut is tightened in place to lock that solenoid in. Each solenoid has a pair of wires going to the circuit board at the bottom of the head assembly, which then connects via ribbon cable to the circuit boards inside the printer stand.
I started by removing the two screws to free the circuit board on the bottom of the print head, then carefully loosened the jamb nuts for each solenoid using a tiny wrench set I have. After that, I started using trial and error to find the offending solenoid by first turning each one counter clockwise to get them moving, then adjusting clockwise, as they were TIGHT, and I was afraid of slipping with the pliers, damaging the wiring, or actually breaking them. Eventually I found the right one, and adjusted it in so that one pin was then even with the rest again. In hindsight, there may have been a reason it was like that, but oh well.
Here’s where things got interesting: I went to do a test print to observe the pin action using the jewelers loop, and found that the printer was erroring out. I realized after some time that the carriage had a pre-set “parking” position, determined by the encoder wheel on the back of the carriage motor. This meant that the carriage had to be attached to the belt at exactly where it originally was. Woof! I managed to do this by finding the impression of the print head on the belt, lined up the carriage assembly to it, and attached the carriage assembly to the belt using a couple tiny binder clips. Whew! Thankfully that worked and the printer was happy printing again (with the print head in my hand).
Now with a better view, I realized that even though the pin was even with the rest, it was still “dead”, so this is likely an electrical issue.