Service manual

EPSON Stylus Photo 870/1270 Revision B
OPERATING PRINCIPLES Electrical Circuit Operating Principles 52
attached on the Gear 76 to detect paper feed amount.
The loop scale encoder sensor outputs two kinds of TTL level pulses
Phase A and Phase B to ASIC (IC8).
Figure 2-19. Loop Scale Encoder Pulse
2.2.2.4 ASF/Pump Motor Driver Circuit
ASF/Pump motor is a PM type stepping motor. The block diagram for the
ASF/Pump motor is as shown below:
Figure 2-20. ASF/Pump Motor Circuit Block Diagram
+
-
+
-
op25
Comparators
Photo
Diodes
Phase B
Phase A
1/1440”
1/5760“
Forward Rotation
(Clockwise)
Backward Rotation
(Counterclockwise)
Phase A
Phase A
Phase B
Phase B
LED
Lens
Photo
Diodes
Comparators
B
A
A
B
IC12
LB11847
+42V
OUTA
OUTA
OUTB
OUTB
ASF-A
ASF-A
ASF-B
ASF-B
+42
C79
100U
C75
0.1U
VBB
C69
0.1U
VCC
GND
PHASE1
PHASE2
ENABLE1
ENABLE2
SWA2
CN6
ASF SENSOR
PFPHAA
PFPHAB
PFENBA
PFENBB
DA0
-
+
IC22
SN104B00PSR
VREF1
VREF2
DATA Bus
Current control signals
IC8
E05B70CD
IC15
C90A13CA