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Troubleshoot common dot matrix printer problems

Brien M Posey Tech Republic

Published: 07 May 2003 09:46 BST

These days, you see fewer and fewer dot matrix printers in corporate environments. However, there are situations where dot matrix printers are still essential, such as when printing on carbon copy forms.

Because dot matrix printers are so scarce these days, you've probably never touched one. But someday, someone may ask you to fix one. Fortunately, these prehistoric beasts aren't that complicated to figure out; although, it helps if you have an understanding of the most common dot matrix printer problems and how to solve them. It's also good to have a few tricks up your sleeve for finding replacement parts and/or printers.

Mystery paper jams
In my experience, the mystery paper jam, a jam with no obvious cause, is by far the most common dot matrix problem. These jams are often caused by a small piece of paper lodged beneath the rollers or beneath the tractor feed. While you can easily remove the rollers on most printers, it's often easier to go fishing with an unbent paper clip or similar extraction tool.

You will often see this problem after the printer has "eaten" a piece of paper. A large chunk of paper gets trapped under the rollers and then gets bunched up by the printer's motion, preventing other sheets from passing through the printer. The problem can also occur if, when printing labels, a label separates from the backing and sticks to the rollers.

Mystery jams can also occur when the tractor feed edges separate from the page while printing. Sometimes this can be a fluke, but other times it may point to a mechanical problem. Try taking the paper out of the printer and hitting the form feed button a few times. Watch the printer's tractor feeds to make sure they are moving and are in synch with each other. Some printers use belts to move the tractor feeds and, over time, these belts wear, break, or become misaligned.

White lines in printed text or graphics
Probably the second most common problem with dot matrix printers is the appearance of horizontal white lines in the middle of printed text or graphics. This almost always signals a problem with the print head. Usually, a pin in the print head has stopped working. I recommend making sure that the print head data ribbon -- not the ink ribbon -- is connected tightly to the print head. If that checks out, try cleaning the print head with alcohol. Sometimes residue can cause a pin to malfunction. If neither of these tricks solves the problem, you will likely have to replace the print head.

Carriage movement but no printing
When a dot matrix printer's carriage moves and the printer makes noise but nothing is printed, it usually means the ink ribbon is dried up or missing. If you know the ribbon is good, watch it while printing. The print head should strike the ribbon as printing occurs. Furthermore, each time the print head returns, the printer should advance the ink ribbon. If this isn't happening, the ink ribbon may be installed incorrectly.