Genicom MatrixPrinter LA36 - Manual (Page 124)

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5.3.8 Fire check control
Figure 5.38 shows fire check circuits. The fire check protects the carriage motor (SP motor), paper feed motor
(LF motor), and color ribbon shift motor (option) from burning out if the control or drive circuit malfunctions.
Two types of fire check detections are used –– short-mode detection for an abnormal large current and long-
mode detection for abnormal forcible excitation.
(1) Short-mode detection
a. Detection circuit
Unusually large currents in the SP and LF motors are detected as an analog signal and output to the fire
check circuit for conversion to an ON or OFF signal.
b. Time constant circuit
The converted ON/OFF signal passes through the time constant circuit where the waveform is shaped and
the compare signal is output to the compare circuit.
c. Compare circuit
If the compare signal voltage exceeds the standard voltage of the compare circuit, the SPALMS or LFALMS
alarm signal is issued from the compare circuit to HDLSI (MBCU20050).
d. HDLSI
HDLSI outputs the PWSTOP signal to the power supply after recognizing that the alarm signal is received.
When the PWSTOP signal is output, the power supply unit (+34 V and +5 V circuits) is turned off to keep
the SP, LF, and color ribbon shift motors from burning out.
For the color ribbon shift motor (option), the detection circuit shares short mode with the SP motor. Shift
motor excitation is detected in item a, above. A fire check alarm error occurs only when an abnormal
excitation length occurs in the time constant circuit in item b, above.
(2) Long-mode detection
a. Detection circuit
Excitation of SP and LF motors is detected as an analog signal and output to the compare circuit.
b. Time constant circuit
The converted ON/OFF signal passes through the time constant circuit where the waveform is shaped and
the compare signal is output to the compare circuit.
c. Compare circuit
In forced excitation, if the analog signal voltage exceeds the standard voltage in the compare circuit, the
SPALML or LFALML alarm signal is issued from the compare circuit to HDLSI (MBCU20050).