This »Maintenance Manual« is an original service guide
of the OKI Data Corporation, Japan.
Do not use the spare parts list in this »Maintenance
Manual«, it is only listed for the sake of completeness.
If you want to order spare parts use only the
spare parts lists in the German »Service Training
Manuals« or in the separate spare parts list of the
OKI Systems (Deutschland) GmbH.
Wichtiger Hinweis!
Dieses »Maintenance Manual« ist ein OriginalService-Handbuch der OKI Data Corporation, Japan.
Verwenden Sie nicht die Ersatzteilliste in diesem
»Maintenance Manual«, sie ist nur der Vollständigkeit
halber aufgeführt.
Benutzen Sie für Ersatzteilbestellungen ausschließlich
die Ersatzteillisten in den deutschen »Service Training
Manuals« oder in den separaten Ersatzteillisten der
OKI Systems (Deutschland) GmbH.
M-OSD-21002-10
Page 2
OKIPAGE4m
LED Page Printer
Troubleshooting Manual
with Component Parts List
(OEL)
APPROVAL
All specifications are subject to change without notice.
This manual has been written to provide guidance for troubleshooting of the OKIPAGE4m 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 if necessary.
Note:
1.High voltage power supply board and power supply unit 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.TOOLS
For troubleshooting the printer, the tools listed below may be needed in addition to general
maintenance tools.
OscilloscopeFrequency response 100 MHz or higher
Soldering ironA slender tip type, 15-20 watts
Ectension code kitP/N : 40105501
ToolRemarks
- 1 -
Page 5
3.CIRCUIT DESCRIPTION
3.1Outline
The circuit of OKIPAGE4m consists of a main control board, a high voltage power supply board
and a power supply unit. The block diagram is shown in Fig. 3-1. The main control board controls
the reception and transmission of data with a host I/f and processes command analysis, bit image
development, raster buffer read. It also controls the engine and high voltage outputs.
(1) Reception and transmission control
The main control board has parallel I/F port which is compliant to the IEEE 1284 specification
and serial I/F (Macintosh I/F) port which is compliant to the RS-422 specification.
An interface task stores all data received from the host into a receive buffer first, and returns
the printer status upon request of the host.
(2) Command analysis processing
The OKIPAGE4m printer has the following emulation mode.
Hiper-W: OKI original
An edit task fetches data from the receive buffer, analizes commands, and sets I/O registers.
(3) Raster data processing
The decompression circuit in the CPU expands the compressed data and stores the data into
the raster buffer.
(4) Raster data transfer
The LED head control circuit in the CPU sends the data stored in the raster buffer to the LED
head.
(5) High voltage control
The high voltage control circuit in the CPU.
The high voltage power supply board generates high voltage outputs, and have sensors, LED for
display.
The power supply unit generates +24VDC output, +5DC output.
- 2 -
Page 6
10MHz
CPU
(MSM65917)
EEPROM
Parallel
I/F
Mac
I/F
Figure 3-1 OKIPAGE4w Block Diagram
Driver
IC
LED head
A8 ~ A15
AD0 ~ AD7
Address
latch
A0 ~ A7
MASKROM
(128 KByte)
OE
CS
D0 ~ D7
CN
Parallel
I/F
LS07
LED headLED head
Main motor
Driver
Parallel
I/F
M
Main motor
- 3 -
Main motor
Electromagnetic
5V
clutch
Sensors
TEMP
TR-VSEN
TR-ISEN
Reset
circuit
5V
0VL
Driver
A0 ~ A10
D0 ~ D3
D-RAM
(512 KByte)
LED
HEAT ON
<Main Control Board>
Option RAM Board
D-RAM
(2MByte)
Option
High-voltage power I/F
HEAT ON
Electromagnetic
High-voltage
clutch
LED
Sensors
TEMP
power
TR-VSEN
TR-ISEN
Driver
+24V
+5V
0VL
0VP
Driver
Manual feed sensor
LED
Paper sensor
Outlet sensor
Toner sensor
Cover open switch
HIgh voltage
power
supply
<High-voltage Power Supply Board>
AC output ON/OFF
Switching
power supply
<Power Supply Unit>
Electromagnetic
clutch
Thermistor
EP cartridge
Heater
(Halogen lamp)
AC
(120 V/230 V)
Page 7
3.2CPU and Memory
(1) CPU (MSM65917)
CPU corenX-8
CPU clock10 MHz
Data bus widthExternal 8 bits, Internal 8 bits
(2) Program ROM
ROM capacity128k-bytes (1-Mbit MASKROM)
ROM type1 Mbits (128k x 8 bits)
Access time150 nsec
When mask ROM in the CPU is valid, the EPROM is not mounted.
(3) Resident RAM
RAM capacity512k bytes (1M x 4 bits D-RAM one piece)
RAM type4M bits (1M x 4 bits)
Access time70 ns
The block diagram of CPU and memory circuit is shown in Fig. 3-2.
- 4 -
Page 8
CPU
IC 6
ALE
RDN
ROCS
DA10
DWR
CAS
AD00 to AD07
LS373
IC3
A08 to A15
DD00 to DD03
DA00 to DA09
A00 to A07
IC2
MASKROM
(128k x 8 bits)
IC11
DRAM
(512k x 4 bits)
RAS0
RAS1
RAS2
Main Control Board
Figure 3-2 Block Diagram of CPU & Memory in OKIPAGE4m
- 5 -
Page 9
3.3Reset Control
When power is turned on, RST-N signal is generated by IC5.
+5V+5V
+5V
Power ON
IC5
1
3
2
Power OFF
63
CPU
RSTN
RST-N
- 6 -
Page 10
3.4EEPROM Control
The BR93LC46A on the main control board is an electrical erasable/programmable ROM of 64bit x 16-bit configuration. Data input to and output from the ROM are bidirectionally transferred
in units of 16 bits through I/O port (EEPRMDT-P) in serial transmission synchronized with a clock
signal from the CPU.
The EEPROM operates in the following instruction modes.
InstructionStart bitOperationAddressData
Read (READ)110A5 to A0
Write Enabled (WEN)10011XXXX
Write (WRITE)101A5 to A0D15 to D0
Write All Address (WRAL)10001XXXXD15 to D0
Write Disabled (WDS)10000XXXX
Erase111A5 to A0
Chip Erasable (ERAL)10010XXXX
CPU
39
38
37
EEPRMDT-P
EEPRMCS-P
EEPRMCLK-P
code
3
DIDO
EEPROM
1
CS
IC4
4
SK
2
Write cycle timing (WRITE)
CS
SK
DI
DO
12491025
10 1
HIGH-Z
Read cycle timing (READ)
CS
SK
DI
DO
HIGH-Z
12
110
A5A4A1A0 D15
4
A5 A4A1A0
910
- 7 -
Min. 450 ns
D14
D15 D14D1 D00D15 D14
D1 D0
Max. 500 ns
BUSY READY
Max. 10 ms
2526
STATUS
Page 11
3.5Parallel Interface
Parallel data is received from a host system via parallel interface which is compliant to the
IEEE1284 specification.
CPU
65 to 68, 71 to 74
64
78
77
79
80
81
82
83
84
PDATA1-P to PDATA8-P
PSTB-N
BUSY-P
ACK-N
PE-P
SEL-P
FAULT-N
IPRIME-N
SELIN-N
AUTOFD-N
IC7
2 to 9
11
10
12
13
32
31
36
14
1
CN4
DATA8-P
to
DATA1-P
STB-N
BUSY-P
ACK-N
PE-P
SEL-P
FAULT-N
IPRIME-N
SELIN-N
AUTOFEED-N
+5V
+5V
18
Compatible mode
The CPU sets a BUSY-P signal to ON at the same time when it reads the parallel data (PDATA1P to PDATA 8-P) from the parallel port at the fall of PSTB-N signal. Furthermore, it makes the
store processing of received data into a receive buffer terminate within a certain fixed time and
outputs an ACK-N signal, setting the BUSY-P signal to OFF.
PARALLEL DATA
(DATA BITs 1 to 8)
0.5 µs min.
DATA STROBE
0.5 µs min.
0.5 µs max.
BUSY
0 min.
ACKNOWLEDGE
0.5 µs to 10 µs
0.5 µs min.
0.5 µs min.
0 min.
0 min.
0 min.
- 8 -
Page 12
3.6Macintosh Interface
Serial data is received from a host system via Macintosh Interface which is compliant to the RS422
specification.
CN5
XCLK-N
TXD+
CPU
86
XCLK-PXCLK-N
85
TXD-P
102
RXD-P
1.2µs approx.
TXD-
TXD+
RXD+
RXD-
1
6
3
8
5
TXD-
RXD+
RXD-
- 9 -
Page 13
3.7LED Lamp Control
There is an LED lamp on the high voltage power supply board which is connected to and controled
by the CPU on the main control board.
The light from the LED lamp can be seen on the Lens Cover through the LED Lens.
CN1
main control boardhigh voltage power supply board
CPU
LED-P
41
CN1
- 10 -
Page 14
3.8LED Head Control
When a paper form is made to arrive at the data write position on print start, the sending of data
to the LED head starts as synchronized with the page synchronous signal/line synchronous signal
(CPU internal signal).
Bit image data developed on the raster buffer in the CPU are DMA-transferred to the register of
a video interface controller (CPU built-in) and then sent to the shift register of the LED head in a
serial transmission synchronized with the VCLK-P signal by the VD0-P signal.
When 1-dot line data (2560 bits) is completely shifted, it is latched by means of the VLD-P signal,
causing LEDs to be driven by the VSTB1-N through VSTB4-N signals in different timing for each
signal.
Some of LED heads have 2496 dots rather than 2560 dots. The controls regarding the number
of dots are adjusted to the LED head installed when the printer is shipped from the factory.
Main control board
CPU
CN6 CN1
LED Head
VCLK-P
VD0-P
VLD-P
VSTB 1-N
VSTB 2-N
VSTB 3-N
VSTB 4-N
+5V
0V
90
89
91
92
93
94
95
Chip 40
64 bit shift REG
LATCH
Bit 2560
Chip 1
1 to 640 bits
641 to 1280
1281 to 1920
1921 to 2560
Bit 1
- 11 -
Page 15
Page
synchronous
signal*
Line
synchronous
signal*
VDT-P
3.33 msec
VCLK-P
VDT-P
VCLK-P
VDT-P
VLD-P
VSTB1-N
VSTB2-N
VSTB3-N
VSTB4-N
* CPU internal signal
8 bits
8 bits
0.2 µs
2560 bits
- 12 -
Page 16
3.9Motor and clutch control
The electromagnetic clutch is driven by a control signal from the CPU and the drive circuit shown
below.
The main motor is driven by the control signals from the CPU and the driver IC.
CPU
DMP1
DMP2
DMP3
0V0V
+5V
96
97
98
+5V
IC10
27
18
26
19
ENA A
To Out3, 4Logic
DECAY
PHASE APHASE B
CN7
GATE CIRCUIT
M
Main Motor
+24VOPEN
37 1141224
Out2Out3
Out1
SW1SW3
SW1SW3
8
Out4Vmm A Vmm B
ALARM
120℃140℃
ENA B
GATE CIRCUIT
Signal of
DECACY
16
17
+5V
+5V+24V
RMON
99
(1) Main motor
+5V
0V
25
BRUNK
0V
0V
SW4SW2
Current
Q
-
R
+
S
Sensor
OSC
Vref AVref B
Vs AVs BRs ARs BLG A PG LG B
23222815 102120TAB5
CN8
Electromagnetic clutch
0VP
0V
SW4SW2
Current
Sensor
RQ
+
S
DMON-P
DMPH1-P
DMPH2-P
Rotation
T0T1T2 T3
Forward rotation
Reverse rotationStop
Operation at normal speed: T0 to T3 = 1.515 ms
- 13 -
Page 17
(2) Motor drive control
Time T0 to T3 determines the motor speed, while the phase different direction between
phase signals DMPH1-P and DMPH2-P determines the rotation direction. DMON-P signal
control a motor coil current. According to the polarity of the phase signal, the coil current flow
as follows:
2) +24V → SW3 → motor coil → SW2 → resistor → earth
The drop voltage across the resistor is input to comparator, where it is compared with a
reference voltage. If an overcurrent flows, a limiter operates to maintain it within a certain
fixed current.
(3) Electromagnetic clutch control
Mechanical operation mode is switched by the combination of the clutch status and the
direction of motor rotation.
clutch status
off
off
on
on
rotation direction
Forward
Reverse
Forward
Reverse
operation mode
cleaning
Hopping from manual
feed slot
illegal operation
Hopping from tray
- 14 -
Page 18
3.10Fuser Temperature Control
The temperature change in a heat controller is converted into the electric potential TEMP
corresponding to the change in the resistance value of a thermistor, and the resultant potential
is fed back to the control circuit. The CPU performs ON/OFF control of the HEATON-P signal to
keep the heat roller temperature constant in accordance with the state at which the thermistor
voltage (TEMP) is read into directly by the AD converter of the CPU.
THCHK-N signal is fixed to “0”.
When the paper thickness is set on the menu of the host, the temperature is adjusted to the
targeted thickness accordingly.
Main Control Board
CPU
TEMP
27
AI4
(A/D)
THCHK-N
34
85
HEATON-P
High voltage power
supply board
IC20
5
+
6
-
7
+5V+5V
IC20
3
+
2
-
1
+5V
Thermistor
Heater
HEATON-N
Thermostat
Heat Roller
+5V
ACIN
Power supply unit
- 15 -
Page 19
Flowchart of Thermistor Circuit Check
START
HEATER OFF
Short check timer(t16)set
No
Time-out ?
Short error TEMP ?
Thermistor error check
timer (t2) set
Thermistor disconnection
check timer (t35) set
Heater On
Temperature > Tn
No
No
Yes
Yes
Yes
Tn...T0 =
T2 =
T4 =
Thermistor short error
End
Light
Medium
Heavy
To constant
temperature control
Thermistor
error check timer (t2)
within time
Yes
Thermistor
disconnection check timer
(t35) within time
Yes
t2 =
t16 =
t35 =
90 sec
520 msec
10 sec
No
No
Time-out
A/D value changed?
Yes
- 16 -
No
Fuser error
End
Thermistor disconnection
error
End
Page 20
Temperature
Controlled
Temperature
T
HEATER ON
OFF
Temperature table
THCHK-N
O
Z
Heater control mode
Normal operation
Not used
Time
T
145˚C:
150˚C:
155˚C:
160˚C:
165˚C:
Paper Thickness
light
medium light
medium
medium heavy
heavy
- 17 -
Page 21
3.11Sensor Control
The CPU supervises the state of each sensor every 40 ms.
Main Control BoardHigh Voltage Power Supply Board
CN1CN1
+5V
CPU
Sensor
signal
47
44
46
48
OFF
+5V
+5V
+5V
+5V
TNRSNS-N
PSIN-N
PSOUT-N
WRSNS-N
TransparentShield
PS1
PS2
PS3
PS4
ON
- 18 -
Page 22
3.12Cover Open
When the cover is opened, a cover open microswitch is opened. This makes a CVOPN-N signal
low, thereby the CPU detects that cover is open. Furthermore, opening the cover stops applying
a +5V power to the high voltage power supply part, resulting in stopping all high voltage outputs.
CN1CN1
Main Control Board
CVOPN-N
CPU
+5V
0V
45
Cover closeCover open
CVOPN-N
Cover
Open
Microswitch
+5V
High Voltage Power Supply Board
High
Voltage
Power
Supply
+5V
Part
High
voltage
output
- 19 -
Page 23
3.13Power Supply Part
(1) Power supply unit
An AC power from an inlet is input to Switching Reg. part .AC power is converted to a +24
VDC output and +5 VDC output.
ACIN
F1F2L
FG
N
Filter
Circuit
Power supply unit
+24V
+5V
0V
HEATER
Switching Reg. Part
CONTROLER
HEATON-N
to AC output
Fuse Ratings
AC Input
Fuse
F1
F2
230 V
250 V 6.3 A
250 V 2 A
120 V
125 V 10 A
250 V 2 A
(2) High voltage power supply board
The +5 VDC power supplied to the high voltage power supply part via the cover open
microswitch as source voltage. The high voltage power supply part supplies necessary
voltage for electro-photography print to output terminals CH, DB, SB, TR, and CB according
to a control signal from the CPU. The table on the next page shows the relationship between
control signals and high voltage outputs.
CN1
MainControl BoardHigh Voltage Power Supply Board
TR1PWM-P
55
TR2PWM-P
59
CHPWM-P
56
SDB1-P
53
CPU
52
54
SDB2-P
DBPWM-P
CVOPN-N
45
+5V
CN1
High Voltage
Power Supply
Part
CH
DB
SB
TR
CB
Cover Open
Microswitch
- 20 -
Page 24
Control Signals and High Voltage Outputs
Control signal nameLevelFunction
TR1PWM-P
TR2PWM-P
CHPWM-P
SDB1-P
SDB2-P
DBPWM-P
H/L
(PWM)
L
H/L(PWM)
L
H/L(PWM)
L
H
L
H
L
H/L(PWM)
L
Makes the part put out a power to TR.
+3 to 5 µA
+0.5 to 4 KV
Makes the part put out a -750V power to TR.
Makes the part put out a -1.35 KV power to CH.
Makes the part put out the following power:
+450V or 0V power to SB
+300V power to DB
Makes the part put out the following power:
-450V power to SB
-300V power to DB
+400V power to CB
Makes the part put out the power to SB, DB, CB.
- 21 -
Page 25
4.TROUBLESHOOTING
4.1Troubleshooting Table
(A)High Voltage Power Supply Board
Note:
A malfunction of the power supply is not repaired by an agency. The abnormality to be
treated here is that of sensors only.
FailurePC Display Message
A paper input jams occur frequently.
PAPER
Flowchart
No.
A - 1
INPUT JAM
A paper feed jams occur frequently.
PAPER
A - 2
FEED JAM
A paper-exit jams occur frequently.
PAPER
A - 3
EXIT JAM
A paper size errors occur frequently.A - 4
PAPER
SIZE ERROR
Paper can not be fed from the manual feed slot .A - 5
The message "COVER OPEN" remains displayed on
the PC display.
COVER OPEN
A - 6
The message "TONERLOW" remains displayed on
the PC display.
The message "TONERSNS" remains displayed on
the PC display.
TONER LOW
TONER SENSOR
- 22 -
A - 7
A - 8
Page 26
(B)Main Control Board
FailurePC Display Message
Initialization error and not restored
INITIALIZATION
Flowchart
No.
B - 1
ERROR
Program ROM error
ROM CHECK
B - 2
ERROR
Resident RAM error
RAM CHECK
B - 3
ERROR
EEPROM errorB - 4
EEPROM CHECK
ERROR
Fuser errorB - 5
Watchdog timer timeout occurs frequently.B - 6
FUSER ERROR
WATCHDOG
Data sent through the Parallel I/F cannot
be received.
Data sent through the Macintosh I/F cannot
be received.
TIMER ERROR
INITIALIZATION
ERROR
INITIALIZATION
ERROR
B - 7
B - 8
- 23 -
Page 27
4.2Troubleshooting Flowchart
A-1Paper input jams occur frequently.
• Is PS4 (Write Sensor ) operating normally?
• NoReplace PS4.
▼
• YesIs Pin1 of CN8 in main control board operating normally?
• NoReplace Q4 or Q5 in main control board.
▼
• YesFailure of IC6 (MSM65917) in main control board.
A-2A paper feed jams occur frequently.
• Is PS4 (Write Sensor ) operating normally?
• NoReplace PS4.
▼
• YesIs PS3 (Outlet Sensor ) operating normally?
• NoReplace PS3.
▼
• YesFailure of IC6 (MSM65917) in main control board.
A-3A paper exit jams occur frequently.
• Is PS3 (Outlet Sensor) operating normally?
• NoReplace PS3.
▼
• YesFailure of IC6 (MSM65917) in main control board.
A-4A paper size errors occur frequently.
• Is PS4 (Write Sensor ) operating normally?
• NoReplace PS4.
▼
• YesFailure of IC6 (MSM65917) in main control board.
A-5Paper can not be fed from manual feed slot.
• Is PS2 (Manual Feed Sensor) operating normally?
• NoReplace PS2.
▼
• YesFailure of IC6 (MSM65917) in main control board.
- 24 -
Page 28
A-6The message “COVER OPEN” remains displayed on the PC display.
• Is CVSW (Cover Open Switch) operating normally?
• NoReplace CVSW.
▼
• YesFailure of IC6 (MSM65917) in main control board.
A-7The message “TONERLOW” remains displayed on the PC display.
• Is PS1 (Toner Sensor) operating normally?
• NoReplace PS1.
▼
• YesFailure of IC6 (MSM65917) in main control board.
A-8The message “TONERSNS” remains displayed on the PC display.
• Is PS1 (Toner Sensor) operating normally?
• NoReplace PS1.
▼
• YesFailure of IC6 (MSM65917) in main control board.
- 25 -
Page 29
B-1Initialization error and not restored
• Replace IC2.
▼
• OK?
▼
• NoIs the 10-MHz clock signal being put out to pin 3 of OCS1?
• NoReplace OSC1 (CST 10.0MTW).
▼
• YesFailure of IC6 (MSM65917)
B-2Program ROM error
• Replace IC2.
B-3Resident RAM error
• Are negative pulses being put out to Pin 4 , 23 (RAS0-N , CSA-N) of IC11?
• NoFailure of IC6 (MSM65917)
▼
• YesAre the signals at pins, 9 TO 12 , 14 TO 18 , 5
(DA00-P to DA09-P) of IC11 being changed?
• NoFailure of IC6 (MSM65917)
▼
• YesReplace IC11.
B-4EEPROM error
• Replace IC4.
▼
• OK?
▼
• NoFailure of IC6 (MSM65917)
B-5Fuser error
• Is the heater on?
▼
• NoIs the voltage at Pin 40 (HEATON-P) of IC6(MSM65917) 5V?
• YesReplace Q3 or IC20
▼
• NoFailure of IC6 (MSM65917)
B-6Watchdog timer timeout occurs frequently.
• Replace IC2.
▼
• OK?
▼
• NoFailure of IC6 (MSM65917)
- 26 -
Page 30
B-7Data sent through the Parallel I/F cannot be received.
• Is the signal at Pin 11 (BUSY-P) of CN4 being at low level?
• NoIs the signal at Pin 13 (BUSY-P) of IC7 (7407) changed as shown
below, at data reception?
ON-LINEOFF-LINE
BUSY-PLowHigh
• NoFailure of IC6 (MSM65917)
▼
• YesReplace IC7 (7407).
▼
• YesIs the level of the signal at Pin 1 (STB-N) of CN4 changed at data reception?
• NoMake sure of the connection of I/F cable or the operation of the h ost
computer.
▼
• YesAre the signals at Pin 1 (ACK-N), Pin 9 (FAULT-N) of IC7 (7407) being
respectively at low level and high level in on-line mode?
• NoReplace IC7 (7407).
• OK?
▼
▼
• YesFailure of IC6 (MSM65917)
• No
B-8Data sent through the Macintosh I/F cannot be received.
• Is the signal at Pin 5 of IC9 (7660) -5V?
• NoReplace IC9 (7660)
▼
• YesIs the signal at Pin 2 , 4 of IC8 (DS8925) being altered?
• NoReplace IC6 (65917)
▼
• YesIs the signal at the Pin 6 , 13 , 14 , 15 of IC8 (DS8925) being altered?
• NoReplace IC6 (65917)
▼
• YesIs the signal at Pin 102 of IC6 (65917) being altered?
Main Control Board(HBMC PCB, Rev. 2)4YA4121-2516G003
Option RAM Board(HBRB PCB, Rev. 1)4YA4121-2502G003
High Voltage Power Supply Board (OLHV PCB, Rev.7)4YA4130-1004G1
or
(TLHV PCB, Rev.2)4YA4130-1024G1
Page 43
R506
R508
R507
R509
R516
R517
R518
R524
R523
R504
R505
R529
R525
R532
R531
R530
R534
R536
R535
C519
C518
C521
R515R512
R503
C503
C509
C520
R510
R533
R537
R538
R545
C511
C510
R513
R520
R519
R522
R521
R514
C505
C526
C502
C504
C522
R546R547
R526
C513
C501
C514
C517
C516
R549
R548
R550
R528
R539
R540
R541
R542
R543
C523
C524
C525
R527
C515
C506
67
65
IC3
R33
IC2
IC11
1
2
16
CN9
SP1 :Set A side , (do not chage)
SW1 :DIP SWITCH
SW1-1
C19
R32
C18
C10
R34
R39
R40
C11
R41
15
14
30
2917
Set switch
UP (OFF)
DOWN (ON)
UP (OFF)
SW1-2
DOWN (ON)
Set SW1-1 OFF and SW1-2 OFF. (do not change)
R9
R3
C9
R5
R15
R7
R16
R17
OSC1
R51
C13
R50
C12
C14
R52
Q4D3
SW1
12
R11
R18R19
R56
R55
contents
Auto I/F
conform with SW1-2
Parallel I/F
Macintosh I/F