2.2 POWER SUPPLY OPERATION
The printer can be powered by either of two power supply boards: the 120 V
board or the
220/240 V
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.
Table 2-3. Power Supply Boards
Board
input Voltage
Fuse F1 Rating
103.5 to 132
2.5A / 125 V
198 to 264
1.25A / 250 V
2.2.1 Power Supply
Overview
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
Output Supply Voltage (DC)
Applications
+35 v
MOTOR, CR drive
MOTOR, PF drive
Printhead drive
+5 v
MAIN board logic circuitry
Various sensors
Control panel LEDs
MOTOR, PF hold
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
supply. A +35 V line voltage detector circuit is connected to the switching circuit. This feedback control
arrangement ensures that the +35
supply is kept stabilized.
The + 5
supply is achieved by feeding the
line through the
power supply circuit.
This circuit further steps down the +35
voltage and outputs a stab5
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
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.
2-11
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