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1.
3-4 Checking
the AC. input.
AC. input
consists
of
AC. inlet,
noise
filter
board, power switch
and
power
transformer.
AC. input
reduces
the
voltage
of
the
power supply
from
the wall outlet
and
supplies
the
reduced voltage
to
the
power
supply
board.
AC. input
and
the
power
supply
board
are
connected
to
each
other
with
the
connector S9. (Fig.
19).
Fig.
19
Checking
the AC. input.
a.
Pull out the
power
supply
cord.
b.
Set
the
tester
to
the
Cl
x
1 range.
c.
Connect
both
terminals
of
the
tester
to
both
pins
of
the AC.
inlet.
(Fis.
20).
d.
Turn
on
the
power switch,
the
indicator
of
the
tester
should show
10O.
There
are
no defects on
the AC. input.
lf
the indicator
shows 0Sl,
there
is
a
short-circuit
on
the AC. input.
When
it
shows
-S},
the
fuse
(F601)
is
broken,
the primary winding of
the
power transformer
or
the
other cords
on the AC'
input
are
disconnected.
'lr
Fig.20
2.
Checking
the
fuse
(F601).
a.
Disassemble
the AC.
input.
(Fig. 21).
1.
Pull out the power cord
from
the AC. inlet.
2.
Remove
the
three
screws
forthe
needle bed and
the three plastic
rivets
for
the lower
side
plate (R)
assembly.
3.
Remove
the
two
screws
for
the AC. inlet.
4.
Take
off
the
lower
side
plate (R)
assembly.
5.
Remove
the
screw
of
the cord
presser
plate and
take
off
the
cord
presser
Plate.
6.
Pull out the
noise
filter
board.
b.
Check
the
fuse
(F601)which
is
installed on
the
noise
filter
board.
lf it
is
broken,
replace
the
fuse
(F601)with
a
new
one,
After
replacing
the
fuse,
find
and repair the
cause
of
the
defects.
Then,
turn
on the
power
switch.
*After
replacing
the
fuse, check
the
resistance
between
the
both
pin
of
the
AC.
in
let.
lf
the indicator
of
the
tester shows 10Q,
the AC.
input
is
working correctly.
There
is a short-circuit on the circuit which
is
worked
by the
DC
power
supply including the
power
suppply
board.
Make sure
that
the AC.
input
is
working
correctly
by
checking
the
voltage
for
the connector
S9.
lf
it
shows
0O, there
is
a
short-circuit
on
the AC. input.
lf
it
shows
-O,
there
are some
disconnections on
the other
circuit of
the
AC.
input.
ris.21
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