Electrical Circuit Operation Principles; C265 Psb/Pse Power Supply Board - Epson Stylus COLOR 900 Service Manual

EPSON Stylus COLOR 900/900N

2.3 Electrical Circuit Operation Principles

The EPSON Stylus Color 900/900N contains the following circuit
boards:
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C265 main board
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C265 PSB/PSE board
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C265 Panel Board

2.3.1 C265 PSB/PSE Power Supply Board

The C265 PSB/PSE power supply board uses a switching regulator
system. It coverts AC line voltage into smooth, filtered DC current at two
voltage levels:
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5 VDC for powering the sensors and main logic board
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42 VDC for powering the printhead, carriage motor, paper feed
motor, and pump/ASF motor
There are two versions of the power supply board:
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the PSB or 120 VAC version (for use in the United States)
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the PSE or 220-240 VAC verion (for use abroad)
The power supply board incorporates overvoltage protection to detect
any abnormal rise in output voltage caused by a defect in the circuit. If
the 42 volt output rises to 48 volts, or the 5 volt output rises to 7 volts,
the power supply board shuts itself off. Once it's deactivated, it cannot
recover until you turn the printer off and then back on.
The power supply circuit also includes a voltage drop delay circuit.
When you turn off the printer by pressing the external power button, the
delay circuit keeps the power supply on long enough for the printer to
complete its power-off operations (paper ejection and printhead
capping). After a pre-determined length of time, the power supply shuts
itself off.
See Figure 2-9, which provides a block-diagram schematic of the
power supply.
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The external power switch is only a secondary switch
W A R N I N G
in the power supply circuit. The primary side of the
power supply is always "hot," even when the printer
appears to be off. Always unplug the printer before
servicing.
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Never touch the heat sink on the Q1 FET with your
bare hands. It is not electrically insulated.
Figure 2-8. Component Layout of C265 PSB/PSE Board
Chapter 2 Operating Principles
D a n g e r !
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