Paper Advance Motor Drive Circuit - Epson LQ-870 Service Manual

2.3.5 Paper Advance Motor Drive Circuit

The printer uses a stepping motor to advance the paper. The minimum amount the printer can advance
paper is l/360 inch. The motor is a 2-2 or 1-2 phase, constant-voltage drive motor. P70 to P73 in the
CPU are the control ports for the stepping motor. Paper advance motor phase data is output through
these ports. PFB to PFD are turned on and off in the PU 150 1 according to the phase data the CPU sends.
When the paper advance motor is running, the voltage supplying the coil of the paper advance motor
is i-35 V. When the paper advance motor is not running and is in hold status, the supply voltage to
the coil is +5 V. Switching between these two supply voltages occurs at the PFCOM terminal of the
PU 150 1 when /PFENB is turned on or off.
CPU (1C)
P72
P71
P73
B
Figure 2-23. Paper Advance Motor Drive Circuit
S T K - 6 0 2 2 B ( 2 A )
C l
C2
c 3
PF-BIN C4
P
2-20
PFA PF MOTOR
P F - A
PFB
P F - B
PFCOM
1 o/9/9 1