Epson FX-80 Technical Service Data page 27

TROUBLESHOOTING
POWER
SUPPLY
Printer
will
not turn
On.
Check
the
AC
Fuse
(F1).
If
Fuse
F1
is
open, check
Capacitors C2 and C3
on
AC
Switch Board
for
possible
short.
Check Power
Transformer
(T1) for
shorted windings and check
the inputs and
the outputs
of
the
Diode DB1
for
a possible short
to
ground.
If
Fuse
F1
is
good, apply
power and check
for
120VAC between
pins
1
and
4 of
Connector CN1A.
If
the
120VAC
is
missing, check
the
Power
Switch
(SW1A)and
the
line
cord.
If
the
120VAC
is
present,
check
for
28.0VAC between
pins
1
and
2 of
Con-
nector CN6, and
for
7.6VAC between
pins 3
and
4
of
Con-
nector
CN6.
If
any
of
these voltages
are missing, check
Transformer
T1 by
substitution.
If
the voltages are present,
check
for
36.0V
at
the
cathode
of
Diode'DBL
If
the 36.0V
is
missing, check Diode
DB1
by
substitution.
If
the 36.0V
is
present, check
for
24.0V
at
Test
Point
VP
and
for
5.0V
either
side of Coil L2.
If
any
of
these voltages
are missing, check
the Regulator
(IC1)
by
substitution.
Check
Diodes ZD1 and
ZD2
and check
voltages
and components
associated with
5V
Regulator
Transistors (Q1 and
Q2)
and
Driver
Transistor
(Q3).
Figure 3
Transistor No. Q11 Q10 Q13 Q9 Q14 Q7 Q8 Q12 Q6
Solenoid No.
123456789
If
the collector
of
the
driving transistor has
a
good
wave-
form, check
Printhead
for a possible
damaged
pin or bad
solenoid.
If
the collector waveform
is
missing, check
for
the waveform shown
in
Figure 4
at
the base
of
the proper
driver transistor when
printing.
If
the base waveform
is
good,
check
the
driver transistor.
Also,
check
for
open
solenoid
coil
in
Printhead
or a
broken connection on
the
flat
cable connector
of Printhead.
If
the base waveform
is
miss-
ing,
check
the
related pin on
the IC
driving that transistor
and check
the IC by
substitution.
MICROPROCESSOR
CHIP OPERATION
Check
for 5.0V
at pins
63 and 64
of
Microprocessor
IC
(3B).
If
the 5.0V
is
missing,
refer to the
"Power
Supply"
section
of this Troubleshooting
guide.
Verify that
the clock
oscillator crystals CR-1 and CR-2
are
functioning.
Check
the
waveforms on
pins 30 and
31 of IC
3B and
pins 2
and
3 of
Slave
Microprocessor
IC
<9B).
Check
for a frequency
of
10MHz
at
pins 30 and
31 of IC
3B and
a
frequency
of
1 1
MHz
at
pins 2 and
3 of IC 9B.
If
either of the
oscillators are not functioning, check
the
components
as-
sociated with pins 30 and
31 of IC
3B and
pins 2 and
3 of IC
9B. Also,
check
the
IC associated with
the
oscillator mal-
functioning by
substitution.
PRINTHEAD
Printhead (HD)
is
moving back and
forth but not
printing.
Check
for
24.0V
at
Test Point
VP
and
also check
for 24.0V
at
pins
14,
15
and
16 of
Connector
CN5
as
well as the
collec-
tors of
each
of the
Driver Transistors
(Q6
thru Q14).
If
the
24.0V
is
missing,
refer to the " Power
Supply"
section
of this
Troubleshooting
guide.
If
the 24.0V
is
correct,
check
for
pulses
at pin 36 of Microprocessor
IC
(3B)
while
printing.
If
the pulses
at
pin 36
of IC
3B
are missing, check
IC
3B
by
substitution.
If
pulses
are present, check
voltages and
logic
readings on
Tri-State Inverter IC
(1B).
Also,
check
for
pulses
at
pins 10
thru 16 of IC 1B and
pins
11
and
16
of
Tri-
State Inverter IC
(2C).
If
pulses
are missing, check
pulses
at
IC 3B, pins
1
thru
8
and
pin
16.
If
pulses
are missing,
check
IC
3B
by
substitution.
If
the pulses appear
at pins
1
thru 8
and
pin 16 of IC
3B
and
are missing
at
pins 10 thru 16
of IC
1B,
check
for 5.0V
at pin 9 of IC 1B and check
IC
1B
by
substitution.
If
pulses
are
missing
at pins
11
and
16
of IC
2C,
check
IC
2C
by
substitution.
If
one
or
more
pins
in
Printhead are not functioning,
check
for the
waveform shown
in
Figure
3 at
the collector
of the
Transistors (Q6
thru Q14)
driving the defective
pin.
Check
the collector waveforms
while
printing.
See
the following
table
to find proper
transistor
driving the
applicable
solenoid.
Figure 4
ov
DC
REFERENCE
CARRIAGE
(TIMING BELT)
MOTOR
Carriage (Timing
Belt)
Motor Assembly
(M3)
does
not
move
the Printhead back and
forth.
Check
the operation of the
HP (Home
Position) Sensor
(M1) and
the
PTS
(Position
Tim-
ing Signal)
Sensor
(M2).
Check
the
Sensor
(M1) by monitor-
ing the Logic reading
at
TP Home
while
moving
the head
manually from
home
position
and back
to
home
position.
The
Logic reading should be Low when
the Printhead
is in
the
home
position,
and
be High when
the Printhead
is
away
from
home
position.
If
the probe
reading
is
incorrect, check
components
associated
with pins
1
and
2 of Inverter IC
(8A)
and check
IC
8A
by
substitution.
Check
the
Sensor
M2
by
monitoring
the pulses
at
TP PTS
using a Logic probe
while
manually moving
the Printhead.
If
the pulses
are missing,
check
the adjustment
of the
Sensor
M2
board,
check
the
Logic readings
at
pins
5, 6,
and
1
and
2 of Inverter IC
(7C),
and check
IC
7C
by
substitution.
If
the sensor
circuits are
normal and
the
Motor
M3
still
does
not
run,
check
voltages and waveforms
associated
with
pins
4, 6,
10, 11,
12
and
13 of Tri-State Inverter IC
(8C).
Check
for
24.0V
at
pin
1
of
Driver
(IC2).
Check
voltages and
components
associated with pins
2, 4,
6 and
pins
17, 13,
and
15 of IC2
and check
IC2 by
substitution.
Check
the
resistance
of the
Motor
M3
windings.
Check
for
9.1
ohms
on connector CN4
between
pins 3
and
1,
pins 3 and
2,
pins 6
and
4,
pins 6
and
5.
If
the resistance
of the
Motor
M3
wind-
ings are
incorrect,
check
the
motor
by
substitution.
If
the
waveforms
are missing
at
pins
4
and
6 of IC 8C, check
for
5.0V
at
pins 26 and
40
of Slave Microprocessor
IC (9B) and
also check
for
frequency
of
1 1
MHz
at
pins 2 and
3 of IC 9B.
If
the frequency
is
incorrect,
check
Crystal
CR2
by
substitu-
tion,
and
also check
IC
9B
by
substitution.
16