Eraser Lamp Control Circuit - Kyocera FS-1900 Service Manual

Eraser lamp control circuit

CPU (U201) turns on its #59 pin to H and turns Q215 and Q214 on. Current flows through Q214
and R249, then the eraser lamp, activating the lamp. Current also routes through R251 and R252 as
bled by R251. Point A below is approximately 14.5 V when the eraser lamp is normal. If the eraser
lamp blows out or the connector is not fitted, current goes through only R251 and R252, subsequently
the potential at point A is as high as approximately 24 V. Difference in the potential at point A
where the eraser lamp is normal or not is automatically detected as an error. When anomaly is
detected with the eraser lamp, the detector circuit turns Q216 on and turns ERDEAD* at #60 pin of
CPU (U201) to L. This in turn causes CPU (U201) to determine that the eraser lamp is faulty,
displaying Call service 5300.
CPU
U201
59
ERASE
P37/SOT0CLK
60
ERDEAD*
P40/SCK0
FS-1900
Engine board
Eraser lamp cotrol circuit
Q215
3
2
1
GND
Figure 4-3-7 Eraser lamp control circuit
+24V
3 Q214
1
2 A
R249
R252
Q216
R250
GND
D2207
R251
GND
4-28
Drum board
YC203
ERASEDR
9
2 ERASER
Eraser lamp [board]