HP 416A - Page 81

i
O'
UJ
Symptoms
Instrument oper -
ating but meter
indicator action is
unstable or
erratic (cont ~ d) .
Possible Cause
Trouble in input cir -
cuit (incident or re -
fleeted) (cont ' d) .
Defecti ve filter.
Test Procedure
6 . b (cont'd)
(2) Check DC v olta ges; levels should
be wit hi n ± 10% of those shown in
the schematic .
7 .
If voltages at V2 and C25 outputs are
correct and voltages at C27 and C41
incorrect , probably one of the filters
is defect ive.
a. To test F ilt er 1, disconnect the re -
flected in put ca ble , and leave the i n-
cide nt in pu t cable (Fig. 18). With test
vo lta ge inco ming , t he meter should
i nd i cate steadily on zero. If Filter 1
i s
defect iv e , i nd icat or will be v er y un -
stable around the 0 point .
b .
To test F ilter 2 , both in put cables
should be connected . Under conditions
of 1 00% reflection , if a low reflection
voltage i s in d icate d by the instrument
meter , Filter 2 is defect ive.
c. Before re placing the filters , check the
defective filter for a poss ib le open in
the wirrng . The filters are identified
in F ig. 20 . (Before the cover of Filter 1
can be removed, the tuni n g eye [V9] must
be freed from its holder and moved out
of the way.) Less than 25 ohms should
be measured :
Filter 1 From output (outs i de terminal)
of R 11 to ground .
Across Rl2
Filter 2 From input to ground, (This
measurement may be from the
output side of C25 to ground.
[Qutput terminal of C25 is iden -
tified in step 6b , abovg )
dAoq-e pu-e
6L 1-e~.rds SS/92/01 I -: 1700V<Ht
Remedies
(2) Checkres i stors
and capacitors
of stage in trouble .
Replace any not
within tolerances
given in Table of
Replaceable Par ts.