Spacing; Line Feed; Alarm Circuit; Paper-End Detect Circuit - OKIDATA ML1120 Maintenance Manual

2.2.5 Spacing

The LSI (MG74Q514-131) outputs space motor phase signals (SP_PHA,SP_PHB) when it receives a
spacing command from µCPU. It outputs IPT signals as the dot timing and carriage position detection
timing in sync with these phase signals.
The space motor phase signals (SP_PHA,SP_PHB) are input to the motor driver, which drives the space
motor.
SH_PHA
Motor driver input
SP_PHB

2.2.6 Line feed

The LF motor phase signals (LF_PHA, LF_PHB) from LSI (MG74Q514-131) are input to the motor driver,
which drives the LF motor.
LF_PHA
Motor driver input
LF_PHB

2.2.7 Alarm circuit

(1) High-temperature head alarm
The temperature of the head is monitored by a thermistor embedded in the head to protect the
head coil.
The head temperature will rise after continuous heavy-duty print jobs. Therefore, when the
head rises beyond a specified temperature, a thermal alarm mode will be entered, and after the
current line is printed, the speed for printing the following lines will be decreased. Furthermore,
if the head temperature does not fall, the following lines will be divided into two depending on
the temperature, and printed by single-direction print.
The alarm is detected when the resistance of the thermistor decreases from the rise in the
head temperature and CPU is input in the A/D converter.

2.2.8 Paper-end detect circuit

When paper runs out, the photosensor (PE) goes Hight level and the paper-end signal becomes 1. This
signal is input in CPU which goes on the B lamp.

2.2.9 Power source unit

The power source unit supplies DC+35V and +5V to each section by switching power.
43471801TH Rev.1
Oki Data CONFIDENTIAL
11 /