AL-1217 (serv.man15). Electrical section - Sharp Copying Equipment Service Manual (repair manual). Page 11

AL-1226  ELECTRICAL SECTION  12 - 11

The operation circuit is composed of the key matrix circuit and the dis-
play matrix circuit.

Select signals SELIN 1 –  3 are sent from the CPU of the MCU to the
selector in the operation circuit.

The signals detecting OFF/ON of the key are sent to the CPU as KIN 1
–  2.

The display is controlled by sending the data signal from the CPU of
the MCU, the clock signals, and the latch signals from the ASIC to the
LED driver in the operation circuit.

∗

The basic circuitry is the same as that of Puma.

The I/F circuit is composed of the USB driver and the IEEE1284 driver,
and performs hard interface with the ASIC (MCU PWB).

With the USB driver, the differential signals (analog) of USB are con-
verted into digital signal, which are sent to the ASIC. In the reverse
procedure, interface between the ASIC (engine) and the host is per-
formed.

The IEEE1284 driver is used to perform interface between the ASIC
(engine) and the host.

The carriage unit is provided with the CCD PWB, the inverter PWB,
and the lamps. It scans documents and transfers AD-converted image
data to the ASIC.

The CCD on the CCD PWB employs the color image sensor uPD8861
of 5400 pixels x 3 lines, and scans documents in the main scanning
direction in the resolution of 600dpi/US letter size.

Image data scanned by the CCD are inputted to the AFE (AD9826),
and subject to CDS, amplification, and AD-conversion. Then digital
data are outputted to the MCU PWB and to the ASIC, which performs
image process of the digital data.

The transformer is controlled by the lamp control signal from the MCU
PWB. The transformer output controls lighting of the cool cathode ray
tube.

The DC power circuit directly rectifies the AC power and performs
switching-conversion with the DC/DC converter circuit, and rectifies
and smoothes again to generate a DC voltage. 

The constant voltage control circuit is of +5VEN. +24V and +12V are of
the non-control system by winding from the +5VEN winding.  As shown
in fig (1), +24V, +12V, and +5V are provided with the ON/OFF function
by external signals. +3.3V is outputted from +5VEN to the regulator IC. 

Refer to the block diagram, fig (1). 

fig (1) Block diagram

USB driver
IC401

USB  

connector

 

D -

D+

OE, RCV, VP, VM
Suspend, VMO
VPO

 

 

 

ASIC

Centronics 

connector 

IEEE1284  

driver  

 

IC403  

ASIC

Noise filter

circuit

Rush current

prevention circuit

Rectifying/
smoothing

circuit

Inverter circuit

(Flyback converter system)

Rectifying/

smoothing circuit

(Semiconductor switch)

Rectifying/

smoothing circuit

Rectifying/

smoothing circuit

+12V regulator IC

(with ON/OFF function)

Overcurrent
protection circuit

Control
circuit

Constant-voltage
detection circuit

(Semiconductor switch)

+3.3V

regulator IC