Ca2 Board; St1 Board - Epson Photo PC-750Z Service Manual

EPSON PhotoPC-750Z

2.1.1.2 CA2 board

Major circuits on the CA2 board are following.
Table 2-3. Major Circuits on the CA2 board
No. Name
The optical black section of the CCD extracts
averaged values from the subsequent data to
make the the black level of the CCD output data
uniform for each line. The optical black section of
1 Digital Clamp
the CCD averaged value for each line is taken as
the sum of the value for the previous line multiplied
by the coefficient k and the value of for the current
line multiplied by the coefficient 1-k.
2 Signal Processor Generic name of No.3 to 6 circuits below.
This circuit performs (gamma) correction in order to
maintain a linear relationship between the light
γ
3 correction circuit
input to the camera and the light output from the
picture screen.
4 Color generation circuit This circuit converts the CCD data to RGB signals.
This circuit generates Y, R-Y, and B-Y signals from
5 Matrix circuit
the RGB signal.
Horizon/Perpendicular
6 This circuit generates aperture signal.
Aperture
The AE/AWB carries out computation based on 64-
AE/AWB, AF arithmetic
7 segment screen, and the AF carries out
(computing) circuit
computations based on a 6-segment screen.
This circuit outputs address, RAS, CAS and AS
8 SDRAM Controller data for controlling the SDRAM. It also refreshes
the SDRAM.
9 Communication circuit Generic name of No.10- to 12 circuits below.
The RS-232C can be used for both synchronous
10 USTART circuit
and asynchronous transmission.
11 SIO circuit Interface for the 4-bit microprocessor.
Operating principles
Function
Board Component
No. Name
8-bit parallel input and output makes it possible to
12 PIO/PWM/LCD switch between individual input/output and PWM
input/output.
It generates chroma signal from color difference
13 Digital encorder
signal.
Controls the interface for the externally-connected
14 JPEG control circuit
JPEG IC.

2.1.1.3 ST1 Board

ST1 board has mainly 2 blocks; power supply circuit part and
STROBE(flash) control circuit part.
Table 2-4. ST1 Board
No. IC No.
This IC has PWM type 4-ch switching regulator circuit;
CH1: Digital 5V, analog system (5V, 15V, -7.5V, 5V (A))
CH2: Digital 3.3V
CH3: Analog voltage LCD system, (5V, 12V, 15.5V)
1 IC501
CH4: Back light
This regulator has short-circuit protection circuit and
Mis-operation prevention circuit for low input voltage as
safety circuits.
2 T3101 Pressure rise/fall transformer for Analog output voltage
3 T3103 Pressure rise transformer for LCD drive voltage output
There are 2 blocks in the strobe(flash) control circuit part; Charging
circuit part and Discharging (Light emission) circuit. Each block is
explained on the next page.
Revision A
Function
Function
26