Chapter 5. Circuit Description; Circuit Description - Sharp UX-4000M - UX 4000 B/W Laser Printer Service Manual

CHAPTER 5. CIRCUIT DESCRIPTION

[1] Circuit description

1. General description
The compact design of the control PWB is obtained by using Risc Proc-
essor (CPU) in the main control section and high density printing of
surface mounting parts. Each PWB is independent according to its func-
tion as shown in Fig. 1.
2. PWB configuration
FAN
AC CORD
MOTOR
POWER
SUPPLY
HEATER
PWB
LAMP
TEL/LIU
PWB
LINE CABLE
HOOK
SW
PWB
OPERATION
PANEL PWB
(1) Control PWB
The control PWB controls peripheral PWBs, mechanical parts, trans-
mission, and performs overall control of the unit.
This machine employs a 1-chip modem (FM214) which is installed on
the control PWB.
(2) TEL/LIU and Hook SW PWB
This PWB controls connection of the telephone line to the unit.
(3) Power supply PWB
This PWB provides voltages of +5V, VREG and +24V to the another
PWB.
(4) Panel PWB
The panel PWB allows input of the operation keys.
(5) Printer PWB
This PWB controls the printer mechanical parts.
This PWB employs 8 bit CPU that is installed on printer PWB.
This CPU control a printer mechanical parts.
(6) LCD PWB
This PWB controls the LCD display.
PC
LSU UNIT
PICK UP SOLENOID
PRINTER
PWB
PRINTER MOTOR
TONER SENSOR
THERMAL FUSE UNIT
THERMISTOR
CONTROL
PWB
SPEAKER
TX
CIS
MOTOR
LCD
Fig. 1
3. Operational description
Operational descriptions are given below:
•
Transmission operation
When a document is loaded in standby mode, the state of the docu-
ment sensor is sensed via the ASIC (IC15).
If the sensor signal was on, the motor is started to bring the docu-
ment into the standby position. With depression of the START key in
the off-hook state, transmission takes place.
Then, the procedure is sent out from the modem and the motor is
rotated to move the document down to the scan line. In the scan
processor, the signal scanned by the CIS is sent to the internal im-
age processor and the AD converter to convert the analog signal into
binary data. This binary data is transferred from the scan processor
to the image buffer within the RAM and encoded and stored in the
transmit buffer of the RAM. The data is then converted from parallel
to serial form by the modem where the serial data is modulated and
sent onto the line.
•
Receive operation
There are two ways of starting reception, manual and automatic.
Depression of the START key in the off-hook mode in the case of
manual receive mode, or CI signal detection by the LIU in the auto-
matic receive mode.
First, the CPU(SH2) controls the procedure signals from the modem
to be ready to receive data. When the program goes into phase C,
the serial data from the modem is converted to parallel form in the
modem interface of the 1 fax CPU(SH2) which is stored in the re-
ceive buffer of the RAM. The data in the receive buffer is decoded
software-wise to reproduce it as binary image data in the image buffer.
The data is DMA transferred to the recording processor within the
ASIC (IC15) and sent to the LSU on printer PWB.
CPU (SH2) and ASIC (IC15) control printing data, LSU, main motor,
high-voltage circuit, heater control and fan motor.
•
Copy operation
To make a copy on this facsimile, the COPY key is pressed when the
machine is in stand-by with a document on the document table and
the telephone set is in the on-hook state.
First, depression of the COPY key advances the document to the
scan line. Similar to the transmitting operation, the image signal from
the CIS is converted to a binary signal in the DMA mode via the
reading processor which is then sent to the image buffer of the RAM.
Next, the data is transferred to the ASIC in the DMA mode to send
the image data to the printer PWB in order to print. The copying takes
place as the operation is repeated.
5 – 1
UX-4000MU
FO-2950MU/C