2.1.2.5 Laser Diode Drive

Figure 2-17 shows the laser diode drive circuit. Laser diode emission is controlled by three signals
(LDATA, LDAPC1, and LDAPC2) from the main board (C169 MAIN-B).
The LDATA signal is the laser on/off signal. When it is LOW, the laser emits, and when it is HIGH,
the laser stops emitting. LDATA is the combination of the two signals in the figure below. If the
VIDEO or the FORCED LASER DIODE ON signal is activated (LOW), the LDATA signal will be
active. The VIDEO signal is an image signal sent from the video controller circuit. The FORCED
LASER DIODE ON signal is a laser emission signal to apply the laser beam to the SOS sensor.
The laser diode is forcibly activated after scanner motor M2 turns on. At this time, laser emission
power is adjusted. LDAPC1 and LDAPC2 are the laser emission power adjust signals; they are
analog signals. LDAPC1 is a tuning, and LDAPC2 is a fine tuning.
If any of the following conditions are detected, the printer indicates a laser error:
The LDAPC1 signal or LDAPC2 signal has been out of the specified range while laser power is
adjusted.
SSCAN
LD_CTL
LDAPC1
LDAPC2
L DATA
Main Board
(C169 MAIN-B)
LD
SOS
(PWB-D)
Laser Diode
SOS Sensor
SOS Mirror
Figure 2-17. Laser Diode Drive Circuit
L DATA
Forced Laser Diode ON

VIDEO

from the Video

Controller Circuit

(C169 MAIN-B)

Figure 2-18. LDATA Generation Circuit
Scanner Motor On
LDATA
LDAPC1
LDAPC2
P_CTL
Figure 2-19. Laser Emission Powe r Adjustment Timing
EPL-5500 Service Manual Operating Principles
Rev. B 2-13