Printer and Photocopier Troubleshooting and Repair Collection : Dot matrix printer operation            
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Printer and Photocopier Technology

Dot matrix printer operation

These are the only type of impact printers still in wide use. A set of steel pins - typically between 9 and 24 - strikes the paper through a fabric or carbon film ribbon. The pins are activated by solenoids which are controlled by the printer's control logic. Multiple passes may be used to increase the effective number of pins and improve print quality (letter versus draft mode).

For text, an internal character generator (ROM) converts ASCII codes to pin firing patterns. For arbitrary graphics, the actual bit map is read out and used to control the pin drive.

The paper, carriage, and sometimes ribbon movement use stepper motors. These, their drivers, or interconnect cables, are common problem areas.