Power Supply Operation; Supply Circuit Operation - Epson LG1-1070 Service Manual

2.2 POWER SUPPLY OPERATION

The printer can be powered by either of two power supply boards: the 120 V C062 PSB board or the
220/240 V C062 PSE board. The only difference in the way these two boards operate is in the primary
circuitry. How they work to supply power to the printer is identical. These power boards output the DC
current necessary to drive the printer control circuits and printer drive mechanism. Table 2-3 shows
the input voltages and fuse ratings for these boards.
2.2.1 Power Supply
The power supply board has two power output lines that supply power to the various control circuits
and drive mechanisms. Table 2-4 lists the parts of the printer that run off these two DC output supply
voltages.
Table 2-4. Power Supply Output Voltages and Applications
+35 v
+5 v

2.2.2 Supply Circuit Operation

Figure 2-16 shows the power supply circuitry in block diagram form. AC power feeds into the printer
from the external power source. A filter circuit removes the noise. The AC voltage then undergoes full
wave rectification and is smoothed to produce the direct current supply voltage. This voltage is fed
through a switching circuit and secondary smoothing circuit to produce the stepped down +35 VDC
supply. A +35 V line voltage detector circuit is connected to the switching circuit. This feedback control
arrangement ensures that the +35 VDC supply is kept stabilized.
The + 5 VDC supply is achieved by feeding the +35 VDC line through the -t-5 VDC power supply circuit.
This circuit further steps down the +35 VDC voltage and outputs a stabilized +5 VDC supply.
There are two main features of the power supply circuit. First, the power supply switch is in the
secondary circuitry. When this switch is turned off, the switching circuit is de-energized and output of
the +35 VDC supply stops. However, since the switch is in the secondary circuitry, while the printer
remains plugged into the external AC supply current continues to flow in the primary circuitry, whether
the power supply switch is turned off or on. For this reason, before you perform any maintenance work,
you must disconnect the printer from the external AC power supply by unplugging it from the power
source.
Table 2-3. Power Supply Boards
Board
input Voltage (VAC)
Overview
.
Output Supply Voltage (DC)
103.5 to 132
198 to 264
Applications
MOTOR, CR drive
MOTOR, PF drive
Printhead drive
Various sensors
Control panel LEDs
MOTOR, PF hold
2-11
Fuse F1 Rating
2.5A / 125 V
1.25A / 250 V