PRINT HEAD

TM 11-7025-233-23

2-8. PRINT HEAD

The print head mounts on the carriage and has a circuit board attached. The board

has no test points and is not replaced separately.

Printed characters are formed by the print head. Hammers in the nozzle are

activated to strike the ribbon between them and the paper to imprint dots on the

paper. The character generator on the logic board identifies the dot pattern

needed to form each character and causes the hammers to print them. There are 63

dot positions possible in the 9 x 7 matrix of hammers.

2-9. PAPER FEED

Paper is fed by a stepper motor which advances the paper one step each time it is

energized by logic board circuitry. The platen and spring-loaded pressure rollers

move the paper between them by friction. The platen is gear driven (fig. 2-5).

Paper Driven by Platen Friction

Figure 2-5.

There are three pressure rollers. A roller lever on the left side can be set to

place the two outside rollers in contact with the platen and retract the center

roller, to place the center roller in contact with the platen and retract the two

outside rollers, or to retract all three rollers (fig. 2-6). These positions allow

paper alinement and pressure adjustment for form width and thickness.

2-5