HP 416A - Page 83

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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
correspond i 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 ge
measured at the junction of R99 and
R98 ; the two voltages should be within
± 10% of the same value .
To localize the trouble , it wi 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
• 1 20 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.