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FS-1010
Eraser lamp control circuit
The CPU (U01) turns pin #23 (ERASERN) of U01 to H level, transistors (Q16 and Q14) turns on
consequently, and the 24 V DC given at pin #1 of connector YC05 applies to the eraser lamps. The
eraser lamps thus illuminate as the current flows through the eraser lamp, the pin #2 of connector
YC05, resistors (R75/R76, and R77/R78), and the ground.
Pin #27 (ERRDYN) of the CPU (U01) is wired to the crossing of resistors (R75/R26 and R77/R78)
via resistor (R74). The U01 turns pin #23 (ERASERN) to H level and monitors the input level after
one second. If the eraser lamp is normal, the current flowing through R74 also flows the zener
diode (DZ01), making the voltage at pin #27 to be approximately 3.7 V. On the contrary, if the level
at pin #27 (ERRDYN) is less than 1 V for more than 2 seconds, despite the U01 turns pin #23
(ERASERN) to H level and applying the 24 V DC to pin #1 of connector YC05, the U01 recognizes
that the current is not flowing through the eraser lamp. The LED indicator “Call service
5300” error is then displayed.
Figure 4-3-4 Eraser lamp control circuit
R69
R74
R68
GND
PGND
GND
GND
1
1
2
2
3
3
Q14
2
3
1
ERRDYN
1
2
R75 R76
R77
R78
DZ01
Q16
ERASERN
+24V
ERASPW
C33
Eraser lamp
YC05
P16/ANI6
P25/ASCK0
27
23
CPU
U01
ERASER
Engine board
Eraser lamp cotrol circuit