
CITIZEN
3. Printer Control Circuits
1) SOL1 to SOL9 are solenoid drive circuits of the printer. The transistor array of IC4 (HA13408) is
driven by each signal, PA0 to PA7 and PB0, of IC1.
This drives nine solenoids of the print head, files the print wire, and forms dot matrix characters through
ribbon on the record paper.
2) MOTOR is the drive circuit to move the carriage loaded with solenoids of the printer.
It is controlled by signals from PB1 of IC1, and run / stop of the motor is controlled by IC8 (74LS04)
and IC5 (STA401A).
3) CC, SOL is the solenoid drive circuit to changeover the ribbon for print in red.
It is controlled by signals from PB2 of IC1, and controls solenoids by IC8 (74LS04) and
IC5 (STA401A).
4) LF, SOL is the solenoid drive circuit for paper feed. It is controlled by signals from PB3 of IC1,
and controls solenoids by IC8 (74LS04) and IC5 (ST401A) to make clutch operation for paper feed.
5) DP inputs signals composed by a disc directly connected to the motor shaft with several slits and
a photo-interruptor, fairs waveforms with R8, C1, and Tr1, and inputs signals to PC3 of IC1 as
dot pulse detection signals (DP) through IC7 (74LS04) and IC8 (74LS04).
6) HP inputs signals composed by a disc directly connected to the motor shaft with several slits and
a photo-interruptor, fairs waveforms with R9, C2, and Tr2, and inputs signals to PC6 of IC1 as
home position signals (HP) through IC7 (74LS04). It is generated every 20 dot pulse detection
signals.
7) RP fairs waveforms of signals of the mechanical leaf switch that makes every one stroke of the print
head with R9, C2, and Tr2, and inputs signals to PC7 of IC1 through IC7 (74LS04).
It shows the datum position of home position signals (HP).
Fig. 3-1 Print Control Circuits