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TROUBLESHOOTING
(Continued)
is
not present
at
pin
9
of IC 7D,
check
IC 7B.
It
the
WR
is
present
at
pin
9
of IC
7D,
check
for
a pulse
on
pin
8
of
IC 7D.
If
there
is
a pulse
on
pin
8
of IC
7D,
check
for
a pulse
on
pin
11
of
Latch
IC
(5B).
If
there
is
no
pulse
on
pin
11
of IC
5B,
replace IC 5D.
If
there
is
a pulse
on
pin
11
of IC
5B,
check
for
a
Low
logic
reading
on
pin
1
of IC 5B.
If
pin
1
of
IC
5B
is
not
Low,
check
Flip/Flop IC
(6D).
If
pin
1
of
IC
5B
is
Low, check
IC 5B.
If
there
is
no
pulse
on
pin
8
of IC
7D,
check
for
a pulse
on
pin
5
of IC
6D.
If
there
is
a pulse
at pin
5
of
IC 6D,
check
IC
7D.
If
there
is
no
pulse
at
pin
5
of IC
6D,
check
for
the
ALE
signal
on
pin
1
of IC
5D.
If
the
ALE
signal
is
missing
on
pin
1
of IC
5D,
check
IC 7B.
If
the
ALE
signal
is
present
on
pin
1
of
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
a
drive
pulse
on
the
base
of
the Transistors.
If
the
drive
pulse
is
present,
check
for
a
defective
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
6
of Flip/Flop IC
(9C).
Pin
6
of IC
9C
should
alternate
between
logic
High and
logic
Low
each
time the
On
Line button
is
pressed.
A
logic
Low
at pin
6
of IC
9C
cor-
responds
to
the
On
Line condition.
If
pin
6
of
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
6
of 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
a
logic
Low
at
pin 4 of IC
4D.
If
pin
4
is
not
logic
Low,
check
IC 4D.
If
pin
4
of IC
4D
is
logic
Low,
check
Tran-
sistors
Q18and
Q21.
If
the
Paper Feed Motor
(M1)
is
overheated,
check
for
pulses
at
pins 3
and
5
of
IC
2B when
the
LF
button
is
pressed.
If
the pulses are not present
at
pins 3
and
5
of IC
2B, replace
IC 7B.
If
the pulses are present
at
pins 3
and
5
of
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
a
logic
High
at
pin
1
of
IC
4D.
If
pin
1
of IC
4D
is
not
logic
High,
check
Micro-
computer
IC
(7B).
If
pin
1
is
logic
High,
check
for
a
logic
Low
at
pin 2 of
IC 4D.
If
pin
2
is
not
logic
Low,
check
IC
4D.
If
pin
2
of IC
4D
is
logic
Low,
check
Transistors
Q18
and
Q20.
If
23.4V
is
missing
at
the emitter
of
Q18,
check
for
a
logic
High
at
pin
5
of IC
8D.
If
pin
5
of IC
8D
is
not
logic
High,
replace
IC 7B.
If
pin
5
is
logic
High,
check
for
a
logic
High
at
pin
6
of IC
8D.
If
pin
6
is
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
a
winding
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
a
logic
High
at
pin
9
of
IC 9D.
If
pin
9
of IC
9D
is
not
logic
High,
check
for
a defective
home
position detec-
tor.
If
pin
9
of
IC
9D
is
logic
High,
check
for
a
logic
Low
at
pin
8
of IC
9D.
If
pin
8
of IC
9D
is
logic
Low,
check
IC 7B.
If
pin
8
of IC
9D
is
not
logic
Low, check
IC 9D.
VERIFY
SENSOR
OPERATION
Check
the operation
of
the
Home
Position
Sensor
(Q98)
by
monitoring
pin
9
of
IC
9D
with
a
logic
probe
while the
print
head
is in
the
home
position
and
the
Printer
turned On.
If
pin
9
of 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
of
IC
4D
while
sliding
a piece
of
paper
in
and
out
of
Paper
End Sensor
Switch.
When
the
paper
is
in
behind the
switch,
8
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