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O'
O'
i
Instrument oper-
ating but meter
indicates steadily
toward the low
stop
(cont'
d).
Instability
in
meter
indication when
measuring small re
-
flect
i
ons
(approxi-
mately
3%
or less)
.
416A004-l
10/26/55
Seri~'i
79 a'nd above
Trouble
in the
reflected
channel
(cont
'
d)
.
Hum
voltage
Noise
(
1)
If
the required
voltages
cannot
be ohtained
,
Filter
2
probably
is
defective
.
(2)
If
v
oltages
at C27
and
C41 are
correct,
localize
trouble
as
in
-
dicated in steps
8 and
9
above
.
With
a
h
i
gh
-
impedance vacuum
tube
volt~
meter (Hewlett
-
Packard Model 400A
,
B
•
C
or D). measure
the
AC
ripple voltage.
From pin
3
of
Vl9 to
g
round
the AC
ripple
should be not more
than
•
002
volt.
If
AC
ripple
measures more
than
.
002
volt
:
a.
Check
regulati
on
(see
step
2
of
"HV regulator
notfunctioning"
,
above)
.
b
.
Inspect
ground connections (at
lugs
on rear of
INCIDENT /REFER-
ENCE
and
REFLECTED/PROBE
connectors).
Check the following possible
sources
of
circuit noise
:
a.
Tubes (V3
and
V4)
b.
All plate res
i
stors
(check
resistance
and
that soldered bond
is
good).
c. Check circuit for any loose connection.
d. Check that ground connections (at
lugs on rear of input connectors) are
firm and free from corrosion.
e. Noise pickup from external test equip-
ment tied to the Model 416A by input
cables or ground connections.
a.
If
regulation
not
obtained, clear
trouble.
b. Resolder
,
if
necessary
.
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