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i
CJ'
\Jl
Symptoms
Instrument
op er
-
ating
but meter
indicator action is
unstable
or
erratic
(con
1
t)
Instrument oper
-
ating but meter
indicates ste
a
dily
toward the high
stop
.
Instrument oper-
ating but meter
indicates
steadily
toward the low
stop.
Possible Cause
Trouble
in
the
flip-flop
circuit.
Trouble
i
n
the
i
nciden
t c
hanne
1.
Trouble
in
the
reflected channel.
Test Procedure
9
.
After checking that
the
trouble is not
in Vl5,
remove
Vl5.
Measure the
voltages at the
junctions of
the
re sis
-
tors in the
networks
associated with
the
tw
o sections
of
VIS
,
and compare
correspondi
ng voltages.
The
voltages
at corresponding
junctions should be
within
±
10%
.
For
example
,
measure
the voltage at the
junction
of
R90
and
R91
,
and compare it with
the
vo
lta
g
e
measured at the
junction of R99
and
R98
;
the two voltages should
be
within
±
10%
of the
same value
.
To localize the trouble
,
it w
i
ll be nec
-
essary to arrange
a
te
s
t s
e
t
-
up as
des-
cribed under Adjustments and shown
in
Fig
.
18
.
a
.
D
i
s
connect the reflected
i
nput cable.
b
.
Perform
steps 1 through 5
of
the
Elec
-
trical Full
Scale Adjustment.
The
le
v
el
at
C2
7
should be
approximately
•
120 volt
AC
±.
010
volt,
(
1)
If the voltage at
C2
7 is w
i
thin
±.
010
v
olt
of
.
120
volt
AC
,
the
trouble is in
the subsequent
cir -
cuit; check as indicated
in
steps
8
and 9
.
(2)
If
voltage at
C27
is
off
,
check as
indicated
in
steps 6a and
7a.
To localize the trouble
,
arrange test
set
-
up as described
u
n
der
Adjustments
and shown in Fig
.
18.
a.
Perform step 6b
,
as described
above.
If the
voltage
at C25
is
approximately
•
25 volt
:
b. Perform steps 1 through 11 of the Elec-
trical Full Scale Adjustment.
- -
,
I
dAoq-e pu-e
bl
repds
SS/92/01
Ti-t.OOVvL9
Remedies
9. Replace
·a
ny
de-
fective component.
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