Oki PACEMARK 4410 Service Manual page 33

(6) Head thermistor short/open alarm circuit
The head thermistor voltage is monitored physically. When short or open circuit occurs, the
HDTHALM-N signal is input to the sub LSI (IC18) and read by the MPU. The MPU stops the
printing operation, informs the host of the short/open alarm, and lights the alarm lamp.
When the head is unloaded, the head thermistor becomes open, resulting in this alarm.
(7) SP motor thermal alarm circuit
The voltage at the thermistor, built in the SP motor encoder block, is monitored physically.
When temperature higher than the specified level is detected, the SPTHACM-N signal is input
to the sub LSI (IC18) and read by the MPU. The MPU starts printing with an approx. 0.2 sec.
interval after each line to cool down the printer.
When the temperature becomes lower than the specified, normal printing will be resumed.
(8) Fuse alarm circuit
Fuses are mounted on each of the SP motor and the other pulse motors, including LF motor,
where the voltage level is monitored physically. When one or both of the fuses on the main
control board are blown, the FUSEALM-P signal is input to the sub LSI (IC18) and read by
the MPU. The MPU stops the printing operation, informs the host of the fuse alarm, and lights
the alarm lamp.
(9) Ribbon jam alarm circuit
The rotation detection knob mounted on the ribbon cassette synchronizes with ribbon rotation
and detects the rotation using the sensor. The RBNSEN-P signal from this sensor is input
to the sub LSI (IC17) for the MPU to monitor the rotation. With no rotation for 16 sec. or longer,
the MPU stops the printing operation, informs the host of the ribbon jam, and lights the alarm
lamp.
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