Epson RX-80 - Impact Printer User manual

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MODEL RX-80
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TECHNICAL SERVICE DATA FOR YOUR PRINTER

5j"/M|CCOMPUTERFACTS" EPSON
MODEL RX-80
PRELIMINARY SERVICE CHECKS
This data provides the user with a time-saving service tool
which is designed for quick isolation and repair of printer
malfunctions.
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Check ail interconnecting cables for good connection and
correct hook-up before making service checks.
Replacement or repair of the AC Switch Board, Control
Board, Function Switch Panel Board, or connectors may be
necessary after the malfunction has been isolated.
TEST EQUIPMENT AND TOOLS
TEST EQUIPMENT
Digital Volt/Ohm Meter
Logic Probe
Transistor Tester
TOOLS
Phillips Screwdriver
Small Screwdriver
Needlenose Pliers
9/32" End Wrench
Solvent for Timing Belt
PARTS LIST AND DESCRIPTION
ITEM NO. PART NO. DESCRIPTION
Fuse(1A @250V S10-B10)
Print Head
Timing Belt Motor Assembly
Paper Feed Motor Assembly
Electrolytic Capacitor
6800/iF @50VDC
Electrolytic Capacitor
6800/iF @25VDC
Electrolytic Capacitor
2200/iF ©50VDC
Electrolytic Capacitor
330/iF @10VDC
Transistor 25A1015Y
Regulator Transistor
2SC2516
Regulator Transistor
2SB772
Regulator IC /*PC305C
Regulator IC 78L05A
Bridge Rectifier 3B4B41
Bridge Rectifier 1B4B1
Zener Diode 4.8V H25B-2
Choke Coil (200/iH)
Choke Coil
Power Transformer
F1 X502040020
H1 F401 500000
M1 F31 601 4000
M2 F316016000
C1 X202596820
C2 X202396820
C3 X202592220
C4 X2001 43310
Q23,Q24,Q25 X300101502
Q26 X302251600
Q28 X301 077251
10C X4401 93050
SR1 X440078051
DB1 X340400060
DB2 X340400030
ZD4 X330000059
L1 Y435201003
L2 Y435201002
T1 Y435501300
0PA Howard W. Sams &Co., Inc.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
The listing of any available replacement part herein does not
constitute in any case arecommendation, warranty or guaranty by
Howard W, Sams SCo., Inc., as to the quality and suitability of such
replacement part. The numbers of these parts have been compiled
from information furnished to Howard W. Sams £Co., Inc., by the
manufacturers of the particular type of replacement part listed.
Reproduction or use, without express permission, of editorial or pictorial
content, in any manner, is prohibited. No patent liability is assumed with
respect to the use of the information contained herein.
©1985 Howard W. Santa &Co., Inc.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
Printed in U.S. of America 85CP-14953 DATE 6-85

PRELIMINARY SERVICE CHECKS (Continued)
GENERAL OPERATING INSTRUCTIONS
PRINTER STATUS (SW1) ANI
SW1 On 5LINE FEED STATUS (SW2) Off
1
2
Compressed
Graphics Character Set
Not Compressed
Control Codes
3
4
Beeper Off
12-inch Form Beeper On
11 -inch Form
5
6
Paper Out Sensor Off
USA Paper Out Sensor On
(International Character
7USA
8USA
SW2 On
Set)
(International Character
Set)
(International Character
Set)
Off
1Slashed Zero Regular Zero
2Printer Select On Printer Select Off
3Auto Line Feed with
4
Carriage Return
One inch Skip Over Perf
Line Feed from Host
Normal (No Perf)
PRINTER SELF-TEST
To use the built-in self-test function, put paper in the printer
and hold down the LF (Line Feed) button while turning On
the printer.
ON LINE, FF AND LF BUTTONS
Printer is On Line (Ready to receive data from the computer)
when all three given LED's are On.
The printer is Off Line when only the top green LED is On.
Pressing the On Line button once puts the printer Off Line
and pressing it again puts the printer back On Line.
The printer must be Off Line for the FF (Form Feed) and LF
(Line Feed) buttons to function.
MISCELLANEOUS ADJUSTMENTS
PTS (HEAD POSITION) SENSOR ADJUSTMENT
Connect Channel Aof adual trace scope to pin 10 of IC 9D
and set the horizontal sweep time to .5mSec. Set the scope
to trigger on the positive edge of the waveform. Hold down
the LF button while turning the Printer On to activate the
self printing test mode. Loosen the screw holding the PTS
(Position Timing Signal) Sensor Board on the right side of
the Timing Belt Motor (M2). Use ascrewdriver in the slot
provided to adjust the PTS Sensor Board for apulse width
of approximately 1.67mSec while the Printer is in the self
printing test mode. See Figure 1.
1.67
mSec
Figure 1
HOME POSITION SENSOR ADJUSTMENT
Loosen the screw holding the Home Position Sensor Board.
Use asmall flat screwdriver in the notch provided to adjust
the Home Position Sensor Board. Move the notch to the left
to move the margin left or move the notch to the right to
move the margin right. Install the Ribbon Cartridge and per-
form the self printing test to test the margin position. Re-
peat this test until printing begins at the desired position on
the paper. When the desired position is obtained, tighten
the Home Position Sensor Board mounting screw.
TIMING BELT ADJUSTMENT
Loosen the adjustment screw on the belt tension plate.
Tighten the belt until no more than 1/4 inch movement oc-
curs on the Printhead when it is at either end of the carriage
shaft and the belt is pressed inward. Tighten the adjust-
ment screw on the belt tension plate. Run the Printer in
self-test mode and note the distance between characters.
The distance should be the same.

PRELIMINARY SERVICE CHECKS (Continued)
DISASSEMBLY INSTRUCTIONS
CABINET UPPER CASE REMOVAL
Remove paper feed knob. Remove printer lid. Remove two
screws holding upper case. Disconnect control panel con-
nector and remove upper case.
POWER SUPPLY BOARD REMOVAL
POSITION TIME SENSOR (PTS) REMOVAL
Unsolder four wires from the PTS Sensor board. Remove
one screw holding PTS Sensor to Carriage Motor assembly.
Remove PTS Sensor from Carriage Motor.
TIMING BELT MOTOR REMOVAL
Disconnect power transformer from Power Supply board
and remove one screw holding board and one screw holding
ground lead of power cord and remove the Power Supply
board.
MAIN BOARD REMOVAL
Disconnect ground Connector FG, Connector CN2, and the
Printer Mechanism ribbon cable. Remove three screws
holding Main board to cabinet bottom. Remove two screws
holding heat sink to cabinet bottom. Push back two plastic
retaining tabs and remove Main board from cabinet.
Remove the Printhead. Refer to Printhead removal. Re-
move wire tie from Timing Belt Motor wires. Remove four
screws holding Timing Belt Motor to chassis. Unsolder the
six Timing Belt Motor wires from terminal board located
under Carriage assembly. Timing Belt Motor may now be
removed.
PAPER FEED MOTOR REMOVAL
Unsolder the six Paper Feed Motor wires from terminal
board located under Carriage assembly. Remove two
screws holding Paper Feed Motor to Carriage assembly and
remove motor.
PRINTER MECHANISM REMOVAL
Disconnect printer mechanism ribbon cable from main
board. Remove two screws holding the mechanism to lower
case assembly. Remove one screw on right hand side of
paper feed motor holding ground strip. Slide mechanism
forward and remove from unit.
PRINTHEAD REMOVAL
Slide Printhead to left of carriage to allow access to Print-
head Cable. Disconnect Printhead Cable by pulling the
plastic tab attached to bottom of Printhead Cable. Slide
Printhead to center position for access to Head Lock Lever.
Rotate lever left to release Printhead. Lift Printhead
straight up to remove from Carriage assembly.
HOME POSITION SENSOR REMOVAL
Unsolder three Home Position Sensor wires from Printhead
Connector board. Remove one screw holding Home Posi-
tion Sensor to chassis. Remove Home Position Sensor.
PAPER END ASSEMBLY REMOVAL
Unsolder two wires from Paper End assembly. Unhook
Paper End lever spring from outer paper guide. Bend back
metal tabs holding Paper End ciruit board and remove.
TIMING BELT REMOVAL
Remove Printer mechanism from case. See Disassembly In-
structions. Press downward on the Timing Belt at each side
of the point where belt is attached to Carriage Assembly.
CAUTION: Belt may be held in place with adhesive cement.
If removal is difficult, slide the Carriage Assembly to the
right and over the access hole in the chassis base. Turn the
chassis over. Carefully cut the adhesive seal with arazor
blade and remove the belt from the Carriage Assembly with
needle-nose pliers.
Loosen the screw securing the Belt Tension Plate and
remove the Timing Belt from the belt-driven pulley. Remove
Timing Belt Motor from the Printer base for access to the
belt drive pulley. Remove belt from pulley. Push belt
through opening in right frame and remove belt from
Printer.
Install replacement by reversing the removal procedure.
Before adjusting tension, apply adrop of adhesive cement
where Timing Belt is attached to Carriage Assembly and
allow to dry. See Timing Belt Adjustment in Miscellaneous
Adjustments.
Ill

PRELIMINARY SERVICE CHECKS (Continued)
SERVICE CHECKS
SEE INTERCONNECTING DIAGRAM AND PHOTOS TO MATCH THE NUMBER IN THE
CIRCLES WITH THOSE IN THE FOLLOWING DATA FOR SERVICE CHECKS TO BE PER-
FORMED.
©PRINTER DEAD
(a) Check Fuse F1. If the fuse is open, unplug Connec-
tors CN1 and CN2 and check Power Transformer T1
for shorted windings.
(b) If Power Transformer T1 is good, check Capacitors
C1, C2, C3 and C4 in the power supply for shorts.
Also check Bridge Rectifiers DB1 and DB2 for
shorts.
(c) If Fuse F1 is good, check for 120 VAC between pins
3and 6of Connector CN1 on the AC Switch board.
If 120 VAC is missing, check Power Switch SW1 and
Line Choke L1 on the AC Switch board. Also check
for an open power cord.
(d) If 120 VAC is present at pins 3and 6of Connector
CN1, check the voltages on three secondary wind-
ings of Power Transformer T1 at Connector CN2. If
any of the secondary voltages are missing, check
the power transformer for an open winding.
(e) If the secondary voltages are normal at Connector
CN2, check for approximately 35 VDC at the output
of Bridge Rectifier DB1 and 13 VDC at the output of
Bridge Rectifier DB2. If either voltage is missing,
check for an open bridge rectifier. If the voltages
are normal at the outputs of the bridge rectifiers,
check for 23.5 VDC at the outputof Transistor Q26.
If 23.5 VDC is missing, check Transistors Q24 and
Q25, IC 10C,Zener Diode ZD4, choke L1 and other
components associated with the 23.5 VDC regulator
circuit. Check for 5VDC at the emitter of Transistor
Q23. If the 5VDC is missing, check Regulator Tran-
sistor Q28, Regulator IC SR1, Choke L2 and other
components associated with the 5VDC regulator
circuit.
(f) If the power supply voltages are normal, replace the
Control Board.
(£) PRINTER WILL NOT RECEIVE DATA
(a) Check Connector CN1 from the host Computer for a
bad connection. If Connector CN1 is good, replace
the Control Board.
(?) PRINT HEAD WILL NOT PRINT
(a) Check for 24 VDC at pin 24 of Connector CN4. If the
24 VDC is missing, check the 24 VDC regulated
power supply. If 24 VDC is present at pin 24 of CN4,
unplug Connector CN4 and check the resistance
between pin 24 and pins 19 thru 22 and 25 thru 29 of
Connector CN4. Each solenoid should measure ap-
proximately 22 ohms. If the solenoid circuit is
open, replace the print head assembly.
(b) If the print head checks good, check Connector
CN4. If Connector CN4 is good, replace the Control
Board.
(?) PRINT HEAD HAS (MISSING DOTS
(a) Remove power from the printer. Unplug Connector
CN4 and check the resistance of the print head
solenoids. If any of the solenoids are open, replace
the print head assembly. If the print head solenoids
check good, check the print head wires for possible
defects. If the print head is good, replace the Con-
trol Board.
(i) PAPER FEED MOTOR MALFUNCTIONING
(a) If the Printer will not advance the paper, check for
24 VDC at pin 2of Connector CN4. If the 24 VDC is
missing, check the 24 VDC regulated power supply.
If the power supply checks good, it may be neces-
sary to replace the Control Board. If 24 VDC is pres-
ent at pin 2of Connector CN4, check pins 2, 6, 8, 10
and 12 of CN4 for good connections. If Connector
CN4 is good, check the Paper Feed Motor windings.
If any of the windings are open, replace the Paper
Feed Motor (M1).
(b) If Connector CN4 and the Paper Feed Motor (M2)
check good, check the Control Board and the Func-
tion Switch Panel Board by substitution.
(?) TIMING BELT MOTOR MALFUNCTIONING
(a) If the Timing Belt Motor (M2) does not move the
print head, check for 24 VDC at pin 1of Connector
CN4. if the 24 VDC is missing, check the 24 VDC
regulated power supply. If the power supply is
good, it may be necessary to replace the Control
Board, if 24 VDC is present at pin 1of Connector
CN4, check pins 1, 5, 7, 9and 11 of CN4 for good
connections. If Connector CN4 is good, check the
windings of the Timing Belt Motor. If any of the
windings are open, replace the Timing Belt Motor.
(b) If Connector CN4 and the Timing Belt Motor are
good, check the Control Board by substitution.
(7) FUNCTION BOARD BUTTONS HAVE NO EFFECT
(a) Check the Function Switch Board Connector for
good connections.
(b) Check the Function Switch Board by substitution.
(c) if the Function Switch Board and its Connector are
good, check the Control Board by substitution.
IV

PRELIMINARY SERVICE CHECKS (Continued)
PARALLEL COMPUTER INTERFACE
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PRELIMINARY SERVICE CHECKS (Continued)
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PRELIMINARY SERVICE CHECKS (Continued)
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MAIN BOARD
VIS

PRELIMINARY SERVICE CHECKS (Continued)
PREVENTATIVE MAINTENANCE
ENVIRONMENT
Computers perform best in aclean, cool area that is below 80 degrees Fahrenheit and free of dust and smoke particles. Even
though home Computers are not affected by cigarette smoke as much as commercial Computers are affected, it is better to
maintain asmoke-free area around the Computer. Do not block cabinet vents of any of the Computer system; Computer,
Monitor, Printer, or other power devices.
ELECTRICAL POWER
Variations in the line voltage can affect the Computer. Try to avoid these fluctuations by using an AC receptacle that is on a
power line not used by appliances or other heavy current demand devices. Apower-surge protector, power-line conditioner, or
non-interruptable power supply may be needed to cure the problem. Do not switch power On and Off frequently.
KEYBOARD
Liquids spilled into the Keyboard can ruin it. Immediately after aspill occurs, disconnect the Computer power plug from AC
power outlet. Then, if circuitry or contacts are contaminated, disassemble the Keyboard and carefully rinse the Keyboard
printed circuit board with distilled water and let it dry. Use acotton swab to clean between the keys. Use anon-abrasive con-
tact cleaner and lint-free wipers on accessible connectors and contacts.
DISK DRIVES
Clean the read/write heads of the Disk Drives about once amonth or after 100 hours usage. Use only an approved head clean-
ing kit.
Handle carefully to preserve proper disk head alignment. Asudden bump or jolt to the Disk Drives can knock the disk head out
of alignment. If the disk drive must be transported, place an old disk in slot and close door during transport.
Store disks in their protective covers and never touch the disk surface. Observe the disk handling precautions usually found
on the back of disk protective covers.
PRINTERS
Carefully vacuum the Printer regularly. Wipe surface areas clean using alight all-purpose cleaner. Do not oil the machine.
The oil will collect abrasive grit and dust. The dust will act as ablanket. This can cause components to overheat and fail.
STATIC ELECTRICITY
Static electricity discharge can affect the Computer. In order to minimize the possibility, use anti-static mats, sprays, tools
and materials, and maintain good humidity in the Computer environment.
MONITOR
Use an isolation transformer with any Monitor that does not come as part of the system since some Monitors use aHOT
chassis (chassis connected to one side of the AC line). The face of the Monitor should never be left on for long periods of time
at high brightness level except when pattern is being changed periodically. Use caution when cleaning anti-glare screens, to
preserve the glare-reduction feature.
VIII

SAMSCOMPUTERFACTS EPSON
MODEL RX-80
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PRELIMINARY SERVICE CHECKS
ENCLOSED
INDEX
Page
Block Diagram 9
Disassembly Instructions 32
Exploded View Printer Mechanism 11,12,21,22
Exploded View Tractor Feed 10,23
General Operating Instructions 6
GridTrace Location Guide
Main Board 25
Line Definitions 5
Logic Chart 13,14
Mechanical Parts List 33
Miscellaneous Adjustments 28
Parts List 15,16,17,18
Page
Photos
Control Board 19
Main Board 24,26,27
Power Supply Board 20
Safety Precautions 5
Schematics
IC Pinouts, Terminal Guides 29
Notes 31
Power Supply 4
Printer 2,3,30
Test Equipment 6
Troubleshooting 7,8,9
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SAMS Howard W. Sams &Co., Inc.
tm 4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
The listing of any available replacement part herein does not
constitute in any case arecommendation, warranty or guaranty by
Howard W. Sams &Co., Inc., as to the quality and suitability of such
replacement part. The numbers of these parts have been compiled
from information furnished to Howard W. Sams &Co., Inc., by the
manufacturers of the particular type of replacement part listed.
Reproduction or use, without express permission, of editorial or pictorial
content, in any manner, is prohibited. No patent liability is assumed with
respect to the use of the information contained herein.
©1985 Howard W. Sams &Co., Inc.
4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.
Printed in U.S. of America. 85CP-14953 DATE 6-85

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SAFETY PRECAUTIONS
1. Use an isolation transformer for servicing.
2. Maintain AC line voltage at rated input.
3. Remove AC power from the Printer before servicing or installing electrostatically sensitive devices. Examples of typical
ES devices are integrated circuits and semiconductor "chip" components.
4. Use extreme caution when handling the printed circuit boards. Some semiconductor devices can be damaged easily by
static electricity. Drain off any electrostatic charge on your body by touching aknown earth ground. Wear acommercial-
ly available discharging wrist strap device. This should be removed prior to applying power to the unit under test.
5. Use agrounded-tip, low voltage soldering iron.
6. Use an isolation (times 10) probe on scope.
7. Do not remove or install boards, mechanical or electrical parts, or other peripherals with Printer AC power On.
8. Do not use freon-propelled sprays. These can generate electrical charges sufficient to damage semiconductor devices.
9. This Printer is equipped with agrounded three-pronged AC plug. This plug must fit into agrounded AC power outlet. Do
not defeat the AC plug safety feature.
10. Periodically examine the AC power cord for damaged or cracked insulation.
11. The Printer cabinet is equipped with vents to prevent heat build-up. Never block, cover, or obstruct these vents.
12. Instructions should be given, especially to children, that objects should not be dropped or pushed into the vents of the ^^
cabinet. This could cause shock or equipment damage. \J
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13. Never expose the Printer to water. If exposed to water turn the unit off. Do not place the Printer near possible water <0
sources.
14. Never leave the Printer unattended or plugged into the AC outlet for long periods of time. Remove AC plug from AC outlet ^
during lightning storms. q
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15. Do not allow anything to rest on AC power cord. |2 |J)
16. Unplug AC power cord from outlet before cleaning Printer. xz
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17. Never use liquids or aerosols directly on the Printer. Spray on cloth and then apply to the Printer cabinet. Make sure the °
Printer is disconnected from the AC power line.
LINE DEFINITIONS
ACK Acknowledge
AUTO FEED XT Automatic Line Feed
BUSY Ready
DO thru D8 Data
ERR Error
INIT Initial
LD1 thru LD8 Latched Data
P/S Parallel Select/Serial Select
PE Paper End
PFO thru PF7 Dot Control
RS Reset
SLCT Select
SLCTIN Select In
STROBE Strobe
+5V 5.0 Volts

GENERAL OPERATING INSTRUCTIONS
PRINTER STATUS (SW1) AND LINE FEED STATUS (SW2)
SW1 On Off
1Compressed Not Compressed
2Graphics Character Set Control Codes
3Beeper Off Beeper On
412-inch Form 11-inch Form
5Paper Out Sensor Off Paper Out Sensor On
6USA (International Character
Set)
7USA (International Character
Set)
8USA (International Character
Set)
SW2 On Off
1Slashed Zero Regular Zero
2Printer Select On Printer Select Off
3Auto Line Feed with
Carriage Return Line Feed from Host
4One inch Skip Over Perf Normal (No Perf)
PRINTER SELF-TEST
To use the built-in self-test function, put paper in the printer
and hold down the LF (Line Feed) button while turning On
the printer.
ON LINE, FF AND LF BUTTONS
Printer is On Line (Ready to receive data from the computer)
when all three given LED's are On.
The printer is Off Line when only the top green LED is On.
Pressing the On Line button once puts the printer Off Line
and pressing it again puts the printer back On Line.
The printer must be Off Line for the FF (Form Feed) and LF
(Line Feed) buttons to function.
TEST EQUIPMENT
Test Equipment listed by Manufacturer illustrates typical or equivalent equipment used by SAMS' Engineers to obtain
measurements and is compatible with most types used by field service technicians.
Equipment Name B&KPrecision
Equipment No.
Simpson
Equipment No.
OSCILLOSCOPE 1570A,1590A,1596 454
LOGIC PROBE DP51
LOGIC PULSER DP101
DIGITAL VOM 2830 463,467,470,474
ANALOG VOM 277 260-7
ISOLATION TRANSFORMER TR110,1604,1653,1655
FREQUENCY COUNTER 1803,1805 710
COLOR BAR GENERATOR 121 1A,1248,1251, 1260 431
DISK DRIVE ANALYZER
FUNCTION GENERATOR 3020 420A.420D
HI-VOLTAGE PROBE HV-44 248

TROUBLESHOOTING
PRINTER IS DEAD
If the printer is dead, check for 23.5 Vat the emitter of
Regulator Transistor (Q26). Also, check for 5.0 Vat the emit-
ter of Regulator Transistor (Q23). If either of these voltages
is missing or incorrect, refer to the "Power Supply" section
of this Troubleshooting guide. If the power supply voltages
are normal, refer to the "Microcomputer (CPU) Operation"
section of this Troubleshooting guide.
POWER SUPPLY
Printer will not turn On. Check the AC Line Fuse (F1). If the
Fuse is open, check Electrolytics C1, C2, C3 and C4 for
possible shorts. Also check Bridge Rectifiers (DB1 and
DB2) for possible shorted diodes. Check Power Trans-
former (T1) for shorted windings.
If Fuse F1 is good, check for 120V AC between pins 3 and 6
of Connector CN1A on the AC Switch board. If 120V AC is
missing, check Power Switch (SW1A) and Line Choke (L1A)
on the AC Switch board. Also check for an open power
cord. If 120V AC is present, check the AC voltages on the
three secondary windings of Power Transformer (T1) at Con-
nector CN2. If any of the secondary voltages are missing,
check Power Transformer for an open winding.
Check for approximately 36V at the output of Bridge Rec-
tifier (DB1) and 13.5V at the output of Bridge Rectifier (DB2).
If either voltage is missing, check the associated Bridge
Rectifier for an open diode.
Check for 23.5V at the emitter of Regulator Transistor (Q26).
If the 23.5V is missing, check Error Amp Transistor (Q24),
Regulator Transistor (Q25), Regulator IC (10C), Zener Diode
(ZD4), Choke (L1) and other components associated with
the 23.4V regulator circuit.
Check for 5V at the emitter of Regulator Transistor (Q23). If
the5V is missing, check Regulator Transistor (Q28), Regula-
tor IC (SR1), Choke (L2) and other components associated
with the 5V regulator circuit.
If the reset signal remains Low at pin 28 of IC 7B, check for
aconstant High on pin 11 orpin 12 of IC9B. If neither pin is
High, check IC9B by substitution. If pin 11 of IC9B remains
High, check IC 9B, Resistors R36 and R39, and Capacitor
C6. If pin 12 of IC 9B remains high, check IC 9B, Resistors
R9 and R37, Capacitor C15 and Resistor Network RM1.
Check for the ALE pulses at pin 46 of Microcomputer IC
(7B). If the pulses are missing at pin 9, check the operation
of the clock circuit. If the clock pulses are normal, check IC
7B by substitution. If the Clock pulses, Reset signal and
ALE pulses are good, check the logic probe readings on the
remaining pins of IC 7B. Compare these readings with the
readings shown on the schematic.
PRINTER WILL NOT RECEIVE DATA
Printer will not receive data from the Computer. Set up the
host Computer to send information to the Printer and check
for the STROBE pulses at pin 1of IC 9B. If the STROBE
pules are missing at pin 1of IC 9B, check for pulses at pin 5
of IC 9D. If the pulses are present on pin 5of IC 9D, check
ICs 9B and 9D by substitution. If the STROBE pulses are
missing at pin 5of IC 9D, check Resistors R8 and R38 and
the connection at pin 1of Connector CN1.
If the STROBE pulses are good at pin 1of IC 9B, check for
pulses on the BUSY line (pin 11 of Connector CN1) and on
the ACK line (pin 10 of Connector CN1). If the BUSY pulses
are missing, check for pulses at pin 8of Flip/Flop IC (9C). If
there are no pulses at pin 8, check IC 9C by substitution. If
the pulses are present at pin 8of IC 9C, check for pulses at
pin 10 of IC 9B. If there are no pulses at pin 10 of IC 9B,
check IC 9B and the Microcomputer IC (7B) by substitution.
If there are pulses present at pin 10 of IC 9B, check IC 4D by
substitution. If the ACK pulses are missing, check for
pulses at pin 5of IC 3B. If pulses are present at pin 5, check
IC 3B by substitution. If there are no pulses at pin 5of IC
3B, check IC 7B by substitution.
If the STROBE, BUSY and ACK pulses are present, check IC
7B by substitution.
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MICROCOMPUTER (CPU) OPERATION
Check for 5.0V on pin 43 of Microcomputer IC (7B). If the
5.0V is missing, refer to the "Power Supply" section of this
Troubleshooting guide.
Verify that the clock oscillator is functioning by checking
for a11 MHz waveform on pin 30 of IC7B. If the oscillator is
not functioning, check Crystal CR1 and Capacitors C9 and
C10. If these components check good, check IC 7B by
substitution.
If the oscillator is good, check the operation of the reset cir-
cuit. Connect alogic probe to pin 28 of IC 7B. Turn On the
Printer. Pin 28 should go Low for about 30mSec and then
go High. If there is no reset signal on pin 28 of IC 7B, check
for amomentary High at pin 11 of IC 9B when the Printer is
turned On. If the momentary High is High at pin 11, check
IC 9B by substitution. If amomentary High does not appear
at pin 11 of IC 9B, check for amomentary Low at pin 1of IC
9D. If the momentary Low appears at pin 1, check IC 9D by
substitution. If the momentary Low does not appear at pin
1of IC 9D, check Electrolytic C6, Resistors R36 and R39,
and Diode D3.
PRINT HEAD MALFUNCTIONING
The print head is moving back and forth but is not printing.
With the printer turned On but not printing, check for 23.4V
supplied to the print head solenoids. This voltage can be
measured on one end of Resistor R6. If the 23.4V is miss-
ing, refer to the "Power Supply" section of this Trouble-
shooting guide. If the 23.4V is present, check for pulses at
pin 23 of Microcomputer IC (7B) with the Printer in the self
printing test mode. These pulses can be measured at the
high end of Capacitor C30. If the pulses are missing,
replace IC 7B.
If the pulses are present at pin 23 of IC 7B, check for 5V
peak to peak pulses at the collector of Regulator Transistor
(Q22). If the pulses are missing, check Transistor Q22. If
the pulses are present at the collector of Q22, check for
pulses at pins 2, 5, 6, 9, 12, 15, 16 and 19 of Latch IC (5B). If
the pulses are missing at pins 2, 5, 6, 9, 12, 15, 16 and 19,
check for pulses at pins 3, 4, 7, 8, 13, 14, 17 and 18 of IC 5B.
If these pulses are missing, check IC 7B. If the pulses are
present at pins 3, 4, 7, 8, 13, 14, 17 and 18 of IC 5B, check for
the WR signal pulses at pin 9of IC 7D. Make sure that the
Printer is still in the self printing test mode. If the WR pulse

TROUBLESHOOTING (Continued)
is not present at pin 9of IC 7D, check IC 7B. It the WR is
present at pin 9of IC 7D, check for apulse on pin 8of IC 7D.
If there is apulse on pin 8of IC 7D, check for apulse on pin
11 of Latch IC (5B). If there is no pulse on pin 11 of IC 5B,
replace IC 5D. If there is apulse on pin 11 of IC 5B, check
for aLow logic reading on pin 1of IC 5B. If pin 1of IC 5B is
not Low, check Flip/Flop IC (6D).
If pin 1of IC 5B is Low, check IC 5B. If there is no pulse on
pin 8of IC 7D, check for apulse on pin 5of IC 6D. If there is
apulse at pin 5of IC 6D, check IC 7D. If there is no pulse at
pin 5of IC 6D, check for the ALE signal on pin 1of IC 5D. If
the ALE signal is missing on pin 1of IC 5D, check IC 7B. If
the ALE signal is present on pin 1of IC 5D, replace IC 5D.
If one pin in the print head is not functioning, check for
23.4V at the collector of Driver Transistors (Q1 through Q9)
for the defective pin. Make the voltage measurement with
the Printer turned On but not printing. If the 23.4V is miss-
ing, check the solenoid coil for the defective pin. If 23.4V is
present on the collector of the Transistor, check for adrive
pulse on the base of the Transistors. If the drive pulse is
present, check for adefective Driver Transistor. If there is
no drive pulse on the base of the Driver Transistor, check
the Buffer IC (1 B, 2B or 4D) associated with that Transistor.
If the driver circuit and the solenoid check good, check the
pin on the print head for possible damage.
PAPER FEED MOTOR MALFUNCTIONING
If the printer will not advance the paper, check pins 2, 6, 8,
10 and 12 of Connector CN4 for good connections. If Con-
nector CN4 is good, check the Paper Feed Motor (M1) wind-
ings. If any of the windings are open, replace the Paper
Feed Motor.
If Connector CN4 and Paper Feed Motor check good, turn
the Printer Off and then On again. Press the On Line button
once. The On Line lamp should turn Off. If the On Line
lamp does not turn Off, press the On Line button while
monitoring pin 6of Flip/Flop IC (9C). Pin 6of IC 9C should
alternate between logic High and logic Low each time the
On Line button is pressed. Alogic Low at pin 6of IC 9C cor-
responds to the On Line condition. If pin 6of IC 9C does
not alternate between logic High and logic Low when the
On Line button is pressed, replace IC 9C. If the alternations
do occur at pin 6of IC 9C, check IC 8D.
If the On Line lamp turns Off when the On Line button is
pressed, press the LF (Line Feed) button and check to see if
the Paper Feed Motor (M1) overheats. If the motor is not
overheated, keep pressing the LF button and check for a
logic Low at pin 37 of IC 7B. If pin 37 of IC 7B is not logic
Low, check the function switch panel and the panel connec-
tor. If pin 37 of IC 7B is logic Low, check for 23.4V at the col-
lector of Switch Transistor (Q19). If 23.4V is not present,
check for alogic Low at pin 4of IC 4D. If pin 4is not logic
Low, check IC 4D. If pin 4of IC 4D is logic Low, check Tran-
sistors Q18and Q21.
If the Paper Feed Motor (M1) is overheated, check for pulses
at pins 3and 5of IC 2B when the LF button is pressed. If
the pulses are not present at pins 3and 5of IC 2B, replace
IC 7B. If the pulses are present at pins 3and 5of IC 2B,
check Driver Transistors (Q14 through Q17). If the tran-
sistors check good, check IC 2B.
TIMING BELT (CARRIAGE) MOTOR MALFUNCTIONING
The Timing Belt Motor (M2) does not move the print head
back and forth. Turn the Printer Off and move the print head
to the center of the carriage. Turn the power back On and
see if the print head moves. If the print head does not move,
check for 23.4V at the collector of Switch Transistor (Q18).
If 23.4V is missing at Q18, check for 23.4V at the emitter of
Switch Transistor (Q27). If 23.4V is missing at the emitter of
Q27, see the "Power Supply" section of this Troubleshoot-
ing guide. If 23.4V is present at the emitter of Q27, check
for 23.4V at the emitter of Transistor Q18. If 23.4V is pres-
ent at the emitter of Q18, check for alogic High at pin 1of
IC 4D. If pin 1of IC 4D is not logic High, check Micro-
computer IC (7B). If pin 1is logic High, check for alogic
Low at pin 2of IC 4D. If pin 2is not logic Low, check IC 4D.
If pin 2of IC 4D is logic Low, check Transistors Q18 and
Q20.
If 23.4V is missing at the emitter of Q18, check for alogic
High at pin 5of IC 8D. If pin 5of IC 8D is not logic High,
replace IC 7B. If pin 5is logic High, check for alogic High at
pin 6of IC 8D. If pin 6is not logic High, check IC 8D. If pin 6
of IC 8D is logic High, check Switch Transistor (Q27).
If 23.4V is present at the collector of Q18, check the Timing
Belt Motor (M2) windings. If awinding is open, replace the
Timing Belt Motor. If the Timing Belt Motor windings are
good, check for an overheated Timing Belt Motor. If the
Timing Belt Motor is overheated, check IC 7B. If the motor
is not overheated, check for 4.9V at the collector of
Regulator Transistor (Q23). If 4.9V is present at the collec-
tor of Q23, check Connector CN4 and the printer
mechanism. If the 4.9V is missing at the collector of Q23,
check for 4.9V at the emitter of Q23. If the 4.9V is missing at
the emitter of Q23, see the "Power Supply" section of this
Troubleshooting guide. If 4.9V is present at the emitter of
Q23, check for 4V at the cathode of Zener Diode ZD2. If the
4V is missing at the cathode, replace Zener Diode ZD2. If 4V
is present at the cathode of ZD2, check Transistor Q23.
If the print head moves to the left when the Printer is turned
On, check for alogic High at pin 9of IC 9D. If pin 9of IC 9D
is not logic High, check for adefective home position detec-
tor. If pin 9of IC 9D is logic High, check for alogic Low at
pin 8of IC 9D. If pin 8of IC 9D is logic Low, check IC 7B. If
pin 8of IC 9D is not logic Low, check IC 9D.
VERIFY SENSOR OPERATION
Check the operation of the Home Position Sensor (Q98) by
monitoring pin 9of IC 9D with alogic probe while the print
head is in the home position and the Printer turned On. If
pin 9of IC 9D does not read logic High with the print head in
the home position, the Home Position Sensor is defective.
Check the operation of the head Timing Position Sensor
(Q99) by turning On the Printer and monitoring pin 11 of IC
9D while manually moving theprint head. The logic probe
should indicate pulses at pin'n of IC 9D while the print
head is being moved. If pulses are not present at pin 11 of
IC 9D, the head Timing Position Sensor is defective.
The operation of the Paper End Sensor Switch (SW99) can
be checked by turning On the Printer and monitoring pin 1
1
of IC 4D while sliding apiece of paper in and out of Paper
End Sensor Switch. When the paper is in behind the switch,
8

TROUBLESHOOTING (Continued)
pin 11 of IC 4D should be logic High. When the paper is
removed, pin 11 should be logic Low. If the logic probe
reading is not correct, the Paper End Sensor Switch is
defective.
Voltages, waveforms and logic readings taken with the
Printer on line and not printing unless noted. The self print-
ing test mode was used for readings taken while printing.
Waveforms taken with atriggered scope. The Sweep/Time
switch was in the Calibrate position and the scope input
was set for DC coupling on zero reference waveforms.
Switch to AC coupling input to view waveforms after DC
reference is measured when necessary. Each waveform is
7cm wide with the DC reference voltage given at the bottom
line of each waveform. The sweep time is in /iSec. per cm.
and peak-to-peak voltage reading are given at the end of
each waveform.
Switches SW1 and SW2 were set as shown on the sche-
matic.
FROM
COMPUTER
"
LATCH
PRINTER
STATUS
SWITCHES LATCH
HOME
POSITION
SENSOR
TIMING
SENSOR
MPU
DRIVER PRINT
HEAD
DRIVER PAPER
FEED
-DRIVER CARRIAGE
DRIVE
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BLOCK DIAGRAM

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TRACTOR FEED
10
Courtesy of Epson America, Inc.
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TRACTOR FEED
23

3-2 3-1
5.7 CTP(3x8)
HN0(4)
PRINTER MECHANISM
22
Courtesy of Epson America, Inc.
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PRINTER MECHANISM
11