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OKIPAGE 20
LED Page Printer
Troubleshooting Manual
with Component Parts List
ODA/OEL/INT

All specifications are subject to change without notice.

40692901TH
CONTENTS
1. OUTLINE ............................................................................................................ 1

2. TOOLS................................................................................................................ 1

3. CIRCUIT DESCRIPTION.................................................................................... 2
3.1 Outline ...................................................................................................... 2
3.2 CPU and Memory ..................................................................................... 4
3.3 Reset Control ........................................................................................... 6
3.4 EEPROM Control ..................................................................................... 7
3.5 Centronics Parallel Interface .................................................................... 9
3.6 RS232C Interface ................................................................................... 10
3.7 Operator Panel Control........................................................................... 11
3.8 LED Head Control .................................................................................. 12
3.9 Motor Control .......................................................................................... 14
3.10 Fuser Temperature Control .................................................................... 16
3.11 Fan Motor Control................................................................................... 19
3.12 Sensor Supervision ................................................................................ 21
3.13 Cover Open ............................................................................................ 22
3.14 Power Supply Interface .......................................................................... 23
3.15 Option (2nd/3rd paper feeder and Multi feeder) Interface ...................... 24
3.16 DUPLEX Interface .................................................................................. 25
3.17 Power Supply Board ............................................................................... 26

4. TROUBLESHOOTING...................................................................................... 28
4.1 Troubleshooting Table ............................................................................ 28
4.2 Troubleshooting Flowchart ..................................................................... 32

5. CIRCUIT DIAGRAM ......................................................................................... 48

6. COMPONENT PARTS LIST ............................................................................. 70

APPENDIX A DUPLEX UNIT (OPTION) .......................................................... A-1
1. CIRCUIT DESCRIPTION ...................................................................... A-1
2. TROUBLESHOOTING ..........................................................................A-3
3. CIRCUIT DIAGRAM .............................................................................. A-8
4. COMPONENT PARTS LIST................................................................ A-12

APPENDIX B HIGH CAPACITY SECOND/THIRD PAPER FEEDER (OPTION) ......... B-1
1. CIRCUIT DESCRIPTION ...................................................................... B-1
2. TROUBLESHOOTING ..........................................................................B-3
3. CIRCUIT DIAGRAM .............................................................................. B-7
4. COMPONENT PARTS LIST................................................................ B-10
APPENDIX C MULTI PURPOSE FEEDER (OPTION) .................................... C-1
1. CIRCUIT DESCRIPTION ..................................................................... C-1
2. TROUBLESHOOTING ......................................................................... C-3
3. CIRCUIT DIAGRAM ............................................................................. C-6
4. COMPONENT PARTS LIST................................................................. C-8
1. OUTLINE

This manual has been written to provide guidance for troubleshooting of the OKIPAGE 20 Printer
(primarily for its printed circuit boards), on an assumption that the reader is knowledgeable of the
printer. Read the maintenance manual for this printer P/N 40300001TH if necessary.

Notes:
1. The power supply board containing a high voltage power supply is dangerous. From the
viewpoint of the safety standards, the local repairing of a defective board is not allowed. Thus,
the objects to be locally repaired as a result of troubleshooting are switches and fuses.
2. Replacement of CPU (MHM2029K) is not recommended. If CPU is founded to be defective,
board replacement is suggested.

2. TOOLS

For troubleshooting the printer, the tools listed below may be needed in addition to general
maintenance tools.

Tool Remarks

Oscilloscope Frequency response 100 MHz or higher

Soldering iron A slender tip type, 15-20 Watt

-1-
3. CIRCUIT DESCRIPTION

3.1 Outline

The control board controls the reception of data transferred through a host I/F and processes
command analysis, bit image development, raster buffer read. It also controls the engine and the
operator panel. Its block diagram is shown in Fig. 3-1.

(1) Reception control
The OKIPAGE 20 has one centronics parallel I/F port and one RS-232C serial I/F port.
Two I/F ports which receives data first can be used automatically.
The other I/F port outputs a busy state.
The centronics parallel I/F port can specify the following item when set by the control panel:

PARALLEL SPEED: HIGH/MEDIUM
BI-DIRECTION : ENABLE/DISABLE
I-PRIME : OFF/ON

The RS-232C serial I/F port can specify the following item when set by the control panel.

Flow control : DTRHI/DTRLO/XONXOFF/RBSTXON
Baud rate : 300/600/1200/2400/4800/9600/19200 (Baud)
Data bit : 7/8 (bit)
Minimum busy time : 200/1000 (ms)
Parity : NONE/ODD/EVEN

An interface task stores all data received from the host into a receive buffer first.

(2) Command analysis processing
The OKIPAGE 20 has the following emulation mode.

Laser Jet Series V : Hewlett Packard
Proprinter III XL : IBM
FX : EPSON
PostScript Level 2 : Adobe (Only when the PostScript SIMM is installed additionally.)

An edit task fetches data from the receive buffer, analizes commands, and reconstructs the
data in such a way that print data are aligned from up to down and from right to left; then it writes
the resultant data into a page buffer with such control data as print position coordinate, font
type, etc. added.

(3) Font Processing
When one page editing is finished, a developing task makes an engine start and fetches data
from the page buffer synchronizing with a printing operation; then it developes the fetched data
to a bit map as referring to data from a character generator, and writes the resultant data into
the raster buffer (of band buffer structure).

(4) Raster buffer read.
As controlling the engine operation, an engine task sends data from the raster buffer to the
LED head.

-2-
MAIN BOARD(BOARD - AAA)
FLASH ROM
Module
or DUPLET unit
PS ROM
MULTI feeder
Module
2nd tray 3rd tray
ROM Paper end
sensor
DRAM Paper near end
Module sensor
LSI
BOARD PXC Tray size
DRAM sensor boad

Clutch for
TRANSISTOR CL Regist Roller

Parllel
I/F 7407 Clutch for
TRANSISTOR CL
Hopping Roller

RS232C DRIVER M Hopping Motor
75188 CPU
I/F

DRIVER M Main Motor

OKI
LAN etc.
HSP Operator panel
(option)
Boad
(option) EEPROM

3V 5V +8V -8V 38V LED HEAD

POWER Inlet sensor 1
SUPLY
UNIT paper sensor
(AC120/230V)
Inlet sensor 2

Toner sensor
Outlet sensor LSI
THERMISTOR

COVER 0V
OPEN Sub-CH
SUB CHARGE ROLLER
LOW VOLTAGE SW
CH
GENERATINO DRIVER CHARG ROLLER
CIRCUIT HIGH TR
VOLTAGE TRANSFER ROLLER
DRIVER CIRCUIT DB
DEVELOPPING ROLLER
FILTER CIRCUIT POWER SB
SUPLY TONER SUPLY ROLLER
AC120V/230V

UNIT CB
CLEANING ROLLER
(high voltage)

FAN

HEATOR

Figure 3-1 Block Diagram

-3-
3.2 CPU and Memory

(1) CPU (MHM2029-003K-41)
CPU core : RISC CPU (MIPS R3000 compatible)
CPU clock : 40.5504 MHz
Data bus width : Exterior 32 bits, Interior 32 bits

(2) ROM (HP LaserJet V emulation)
ROM capacity : 6 Mbytes (24-Mbit mask ROM two pieces)
ROM type : 24 Mbits (1.5M x 16 bits)
Access time : 100 ns

(3) Option ROM (SIMM: one slot)
PostScript SIMM or FLASH SIMM

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