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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
a
triggered
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
o
D
CO
o
o m
m 3
"
«
X z
CO
o
BLOCK DIAGRAM
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