Alarm Circuits; Fault Alarm Circuit (In Power Supply Unit); Printhead Overheat Alarm Circuit; Cover Open Alarm Circuit - OKIDATA Pacemark 3410 Service Handbook

2.1.08

Alarm Circuits

Fault Alarm Circuit (in Power Supply Unit)

This protective circuit turns off the power supply when a fault occurs in the printhead, line feed,
or bail motor drive circuits, thus preventing secondary component failure.
To accomplish this, the circuit monitors the overdrive signal of each drive circuit. If the
duration of any drive circuit exceeds a predetermined length of time, the appropriate signal
(EVN COM, ODD COM, LF COM or BM COM) will be sent to the fault alarm circuit. The
fault alarm circuit generates the ALM signal which causes the power supply to turn all DC
power OFF.

Printhead Overheat Alarm Circuit

In order to protect the printhead coils, this circuit monitors the printhead temperature by using a
thermistor contained in the printhead. The CPU senses this circuit every time a line is printed.
When printing, the printhead temperature will increase. If the head temperature reaches
approximately 115° Celsius, a head overheat ALARM 1 is generated. When ALARM 1 is
detected by the MPU, the printer will begin unidirectional printing. If the printhead temperature
increases to 125° Celsius, ALARM 2 is generated and printing is halted until the head
temperature decreases. When the head temperature returns below the ALARM 1 threshold,
printing is resumed.

Cover Open Alarm Circuit

When the front access cover is opened, the CVOPEN-N signal is sent to the MPU from the
cover interlock microswitch. The MPU will halt printing immediately and light the ALARM
Lamp.
2.1.09

Paper End Detection Circuit

NOTE:
Paper End is also known as paper out
Whenever the release lever is in the Tractor (Continuous) Feed position, paper end is detected
by the microswitch on the push tractor (rear feed) or the paper end sensor on the sensor board
(bottom feed).
Whenever the release lever is in the Friction (Sheet) Feed position, Paper End is detected by a
photosensor (top feed) located in the paper pressure guide.
When the printer detects an out of paper condition, the PEN (Paper End) signal goes low, the
printing is stopped and the ALARM LAMP is turned ON.
Principles of Operation 2 - 10 Pacemark 3410