HP 416A - Page 80

g
CJ°'
N
, .
Instrument op er -
ating but meter
indicator action is
unstable or errat ic
(con t ' d) .
·
416A004-l 10/26 / 55 Seria:l 7() a~d abo~e
Trouble in instrument
( cont
1
d }o
Traub le in input cir -
cuit (incident or re-
flected ).
5 . (con
1
d)
capacitors C27 and C41 , as described
in Electrical Full Scale Adjustment .
a. If v oltages at C27 and/or C41 are not
at levels specified i n Electrical Full
Scale Adjustments , trouble is in in-
put circuit (s ee steps 6 and 7).
b . If voltages at C27 and C41 are at spec-
ifie d le vels
9
trouble is in a subse-
quent circuit (see steps 8 and 9),
6 . Under a test condit i on of 100% reflec-
tion (attenuator #2 at 0 db) :
a. From pin 3 of V2 to ground , AC
voltage should be approximately
0
035 volt. If . 035 volt ± 10% is not
obtained , trouble probably is in the
incident channel input cirucit :
( 1)
Check Vl and V2.
(2) Check DC voltages; levels should
be within ±10% of those shown in
the schematic .
b. From the output side of C25 to ground,
AC voltage should be approximately
. 25 volt. ( C25 is mounted on resistor
board RB 1 [Figs . 21 and 22] . The C25
output connection is made at the term-
inal on the inner edge of RB 1 [he side
nearest the vacuum tube socket!] . ) If
. 25 volt ±10% is not obtained , trouble
probably is in the reflected channel in -
put circuit:
( 1) Check V2 , V3, and V4 .
( 1)
Replace Vl or
V 2 , if defective .
(2) Check resistors
and capacitors
of stage in
trouble. Re -
place any not
within toler anc es
given in Table of
Rep lac eab le
Parts .
(
1) Replace V2 , V 3 ,
or V4, if defe c-
tive.