Epson FX-870/1170 - Manual (Page 134)

Principles of Operation
Power Supply Operation
The FX-870/1170 printer is powered by a 120 VAC power supply board (C076 PSB board assembly).
This board outputs the DC current necessary to drive the printer control circuits and the printer
drive mechanism. Fuse
V) is used to protect the power supply circuit of the board
in case of a short circuit.
Table 6-3. Power Supply Input Voltage and Fuse Rating
Input Voltage Fuse Rating
103.5 132 VAC 2.5 V
Power Supply Overview
The power supply board has two power output lines that supply power to the control circuits and
the drive mechanisms. Table 6-4 lists the components (parts or assemblies) of the printer that are
powered by these two DC voltages.
Table 6-4. Power Supply Output Voltages and Applications
Output Voltage (DC) Applications
v CR (carriage) motor drive
PF (paper feed) motor drive
Printhead drive
v Main control board logic circuitry
Sensors
Control panel
PF (paper feed) motor hold
Power Supply Circuit Operation
Figure 6-22 shows the power supply circuitry in block diagram form. When AC power enters the
printer from an external power source, the filter circuit removes the noise. The AC voltage then
undergoes full wave rectification and is smoothed to produce direct current. The voltage is then
fed through the switching circuit and the secondary smoothing circuit to produce a stepped down
VDC voltage. A VDC detector circuit is connected to the switching circuit. This feedback
control arrangement ensures a stable VDC voltage supply.
A VDC voltage is generated by feeding the VDC voltage through the VDC power supply
circuit, where the VDC is stepped down to a stable VDC voltage. The switching regulator
IC containing the control circuits performs this function. It controls the
VDC line output.
Epson FX-87011170 6-19