C378Psb/Pse Board - Epson Stylus COLOR 880 Service Manual

EPSON Stylus COLOR 880

2.2.1 C378PSB/PSE Board

The Stylus COLOR 880 is equipped with the C378PSB/PSE, the common
power supply board for the both products. The basic structure of the circuit is
the same as for the C257PSB/PSE board used in the Stylus COLOR 740. The
power supply boards of these printers use a RCC switching regulator, which
generates +42VDC for drive line and +5VDC for logic line to drive the printer.
For one of the major characteristics of the C378PSB/PSE, it uses the
secondary switch that is also used in the Stylus Color series. Use of the
secondary switch enable the circuit to keep supplying voltage to 5 V line and 24
V line for approximately 30 seconds if the printer power is turned off through
the panel switch. This extra time allows the printer to perform the following
operations when the printer is turned off through the panel switch while it is in
operation.
When the printer is in a printing state, if the CR unit is away from the home
position, the CR unit can return to the home position to be locked before
the printer power shuts down.
When the printer is not in a printing state, if paper fed from ASF remains in
the printer, the paper is ejected before the printer power shuts down.
Table 2-9 in the right column shows the application of each voltage generated
by C378PSB/PSE board.
NOTE: The 5VDC is only applied to the parts and locations shown in the Table 2-9.
The C378MAIN, like the C267MAIN-B board*, uses the 3.3V drive chips for
most of the logic line chips (CPU, ASIC, ROM, DRAM). For this reason, those
chips are not driven by the +5VDC but 3.3VDC that is reduced by the IC9
(3.3VDC regulator) on the C378Main Board.
* Used in the minor changed models of the Stylus COLOR 740, Stylus Pro
750, and Stylus Pro 1200.
Figure 2-15 in the right column shows the block diagram for the C378PSB/PSE
board. The process from the input of AC voltage to the output of 42 V DC and 5
V is explained in the following page.
Operating Principles Electrical Circuit Operating Principles
Table 2-9. Application of the DC Voltages
Voltage Application
CR Motor, ASF/Pump Motor, PF Motor
+42VDC
Head driving power supply
Sensor circuit power supply voltage
LED panel drive power supply
+5VDC
Nozzle selector control signal voltage
I/F Control Circuit
Slave CPU for DC motor control
Figure 2-15. C378PSB/PSE Board Block Diagram
Revision A
43