Epson R1800 - Stylus Photo Color Inkjet Printer, Service Manual

Page: 19 / 234

EPSON Stylus Photo R1800/R2400 Revision B
Operating Principles Printer Mechanism 19
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PW sensor dark voltage (VH) measurement
PW sensor dark voltage (VH) measurement is performed at the following
timings and locations and used to calculate the threshold value of whether
paper is present or not.
„
Cut sheets, Roll paper
The dark voltage is measured and updated at every power-on, and the
threshold value (VS) is calculated and saved in the EPROM area as a
PW detection level.
•
Threshold value detection voltage: Paper present
•
Threshold value detection voltage: Paper absent
„
CD-R Tray
When printing on a CD-R, the dark voltage is measured on the CD-R
tray, and the threshold value (VS) is then calculated and saved in the
EPROM area as a PW detection level.
•
Threshold value detection voltage: CD-R present
(tray home position detected)
The measurement voltage in the presence of the CD-R is saved into
the EEPROM as a white level. The white level value is used to check
the sensor deterioration condition during servicing or like.
• If the measurement value of the white level is close to that of the PW
detection level, it means that the sensor is dirty or deteriorated.
2.2.1.4 APG (Auto PG) Mechanism
The following indicates the specification of the DC motor that drives the APG.
The APG Motor (DC Motor) and two APG Sensors drive the PG Cam to
automatically adjust the PG amount according to the paper.
Figure 2-2. APG Mechanism
Table 2-3. APG Motor Specifications
Item Specifications
Type DC motor with brushes
Drive voltage +42V ± 5% (voltage applied to driver)
Armature resistance 64.7
Ω
± 15%
Inductance 37.6mH ± 25%
Drive method PWM, constant-current chopping
Drive IC A6628
Carriage Shaft Carriage Unit
APG Motor
PG Cam APG Sensor
APG
Sensor