Sanyo DVP-P1EX Service Manual page 3

2-4.Thermal print head
The print head has 1280 dots, and is driven by 10 drivers.
2-5.Sensor section
Pins 1-5 of CN161 are used for the head position sensor.
Chattering is prevented by the Schmidt buffer from CN161.
The sensors are the transmission type, and the cutouts in the
detection part of the head position cam are detected.
When the power supply is turned on, initial operations are car-
ried out.
In the initial operations, the cam is moved 40 degrees (to a
point between paper/ribbon feed and paper supply), paper jams,
etc., detected; if normal, it returns to standby, and if paper is
jammed, it ejects it.
Table 1 shows the relationship between mode and sensor out-
put.
When printing ends normally in the normal manner for comple-
tion, it returns to the standby position.
PAPER
STANDBY
EJECT
H H
S1
S2 H L
H
S3 L
Table 1
CN162 is the ribbon encoding sensor.
It is a transmission sensor, and it detects the ribbon feed; wave-
form shaping is carried out in IC 163.
CN163 is the ribbon top sensor.
It is a reflection sensor, and the start of a color is detected by a
certain black marker on the ribbon. The light generated by the
ribbon sensor is reflected by the light reflecting part of the rib-
bon cassette, and the photo transistor is turned ON, but when
the marker passes by, it absorbs the light, so even if there is
light, it is not reflected and the photo transistor turns OFF, send-
ing out signal H. The markers are placed at the beginning of
each print color, but the manner in which the marker is set is
different for yellow and the other parts (magenta, cyan, OP).
Since this printer prints in the order of yellow, magenta, cyan
and OP, yellow is detected for the starting of printing.
Therefore, the markers and the sensors are positioned so that
yellow is detected by sensor 2, and the others are detected by
sensor 1.
PAPER
PAPER/
PRINT
SUP-
RIBBON
PLY
FEED
L
L H
H L
H
L
L H
yellow
magenta
SENSOR1
SENSOR2
marke marke
Since the detected signal is detected by the reflection sensor
from the ink ribbon, the waveform is indeterminate, and there
may be erroneous operations if it remains as is, so waveform
shaping is performed by a comparator (IC 161).
The arrows displayed on the ink ribbon are for taking up the
slack in the ribbon, and the direction of ribbon winding is in the
order yellow, magenta, cyan and OP in the opposite direction
of the arrows.
CN164 is the paper top sensor.
It is a reflection sensor, and it carries out paper top detection
and detection of the absence or presence of paper.
Along with detecting the top of the paper, it forms the basis for
determining how many pulses after thaSince the top of the pa-
per cannot be detected when there is no paper, this also in-
cludes detection of the absence or presence of paper.
CN165 is the paper eject sensor.
Detection is carried out with the turning ON/OFF of the switch.
− 3 −
cyan OP yellow
marke marke
marke
Fig. 1