Commodore Home Computer Museum (NZ)

Commodore Printers

Early Commodore printers were quite different from the types we know today. The first of the dot-matrix types did NOT have a revolving platen that we accept as 'normal' today. In fact, the 3022P and 4022P printers that were in use with the Commodore PET computers (late 1970s) had only a steel rod with a flat face for the printhead pins to strike against.

In later versions there was a roller (platen) which fed the paper and acted as a striking medium for the head pins to press the ribbon and paper against to create the characters. Some of the early printheads only had 8 pins where the common figure adopted was usually 9 pins. The 'matrix' of dots created the image on paper which was either text or on later printers, graphics also.

The picture at the right shows the general idea, the print-head moves across the page slightly after printing each vertical selection of pin impacts. This particular set of matrix details was taken from an actual printer manual.

animation of early method of creating dot-matrix image

Another version of the dot-matrix arrangement was used which was somewhat unusual but in fact quite effective. With a good ribbon it produced good quality text and graphics which is quite surprising when you look at the arrangement in the picture at left.
The early VIC-1515/1525 style printers (1980/81 vintage) used this arrangement. The print-head consisted of just a single vertical plate which was moved in and out rapidly by signals sent to a coil inside the head. The head contacted the ribbon, pressing it onto the paper which in turn had a splined platen revolving behind it.

A dot was produced at the point where the print-head 'plate' struck the ribbon against one of the horizonal ridges on the revolving platen. This was all controlled by the electronics of the printer. The dot would appear higher or lower depending where exactly the horizontal spline was at the time of impact.

The head return mechanism on some of these printers was nothing more than a spring which stretched out when the head moved to the right, then pulled the head back to the left when it was released at the end of the row. One version had a flat steel clock-type spring while the other had a more conventional type coil spring.

Eventually 24 pin printers evolved and these provided very high quality print by comparison. Later the InkJet printers appeared and were initially quite expensive, these were followed by the Laser printer technology.

Information provided and animated graphics created by Alan Gilchrist.