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 Fl(2.5 A/125 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 Fl Rating

103.5 - 132 VAC

2.5 A/l25 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

I

Output Voltage (DC)Applications

 

 

 

 

+35 v

CR (carriage) motor drive

 

 

PF (paper feed) motor drive

 

 

Printhead drive

 

 

 

 

+5 v

Main control board logic circuitry

 

 

Sensors

 

 

Control panel LEDs

 

 

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 +35 VDC voltage. A +35 VDC detector circuit is connected to the switching circuit. This feedback control arrangement ensures a stable +35 VDC voltage supply.

A +5 VDC voltage is generated by feeding the +35 VDC voltage through the +5 VDC power supply circuit, where the +35 VDC is stepped down to a stable +5 VDC voltage. The switching regulator IC containing the overcurrent/overvoltage control circuits performs this function. It controls the +5 VDC line output.

.

Epson FX-87011170

6-19