C304Main Board - Epson Stylus Photo 870 Service Manual

EPSON Stylus Photo 870/1270
Figure 2-14 shows the block diagram of the C298PSB/PSE board.
+ 4 2 V D C + 5 V D C
I C 5 1
+ 5 V R e g u l a t o r
+ 4 2 V D C L i n e
O v e r V o l t a g e
L i m i t a t i o n
Z D 8 1 - 8 6 , Z D 5 1
+ 4 2 V D C L i n e
C o n s t a n t C o n t r o l
C 5 1
S m o o t h i n g
C i r c u i t
D 5 1
T R A N S ( T 1 )
C 1 1
S m o o t h i n g
C i r c u i t
O v e r C u r r e n t
. i l t e r C i r c i u t
P r o t e c t i o n
. 1 , T H 1 L 1 , C 1 , C 2
A C I n p u t
Figure 2-14. C298PSB/PSE Board Block Diagram
P S C S i g n a l
f r o m M a i n b o a r d
Z D 5 3
+ 5 V D C L i n e
O v e r V o l t a g e
L i m i t a t i o n
Z D 5 2 , 8 7
Z D 9 0
+ 4 2 V D C L i n D r o p
L i m i t a t i o n C i r c u i t
C 8 4 , Q 8 4
P o w e r D r o p
D e l a y C i r c u i t
P C 1
P h o t o
C o u p l e r
Q 1 Q 2 , Q 3 , Q 3 1
A b n o r m a l
M a i n S w i t c h i n g
. e e d b a c k c i r c u i t
C i r c u i t
. u l l W a v e
R e c t i f i e r c i r c u i t
D B 1

2.4.2 C304MAIN Board

The logic circuit of the C304MAIN board is composed of the following:
" Logic line (CPU, ASIC, DRAM, EEPROM, and so on)
" Various motor control/driver circuits (carriage motor, paper
feed motor, and ASF/Pump motor)
" Head control/driver circuits
" Interface control (parallel and USB interfaces)
" Sensor circuits
" Timer circuits
" Reset circuits
This main board is different from other models in the following ways:
! 3.3 V chips in the logic circuit
The 3.3 V regulator on the C304MAIN board produces 3.3 V by
regulating the 5.5 VDC supplied by the power supply board.
Table q lists the chips driven by +5 V and +3 V.
Table 2-8. 3.3 and 5.5 V Chips
+5 V
Sensors
Interface circuit
PNL board
Slave CPU
! Slave CPU
A slave CPU attached to the main board controls the DC motors.
This lets the main CPU and ASIC perform other duties, which
speeds up data processing.
Chapter 2 Technical Overview
3.3 V
CPU
ASIC
P-ROM
D-RAM
15