HP 416A - Unstable or Erratic Meter Indication

i
O'
0
Instrument oper -
ating but meter
indicator action is
uns t able or erratic.
"' t!
416A004-l 10/26/55 Serial 79 and above
Insufficient voltage
at inputs o
L Check RF POWER MONITOR
0
a
0
Tuning eye aperture should be open
not more than approximately 1/4
11
0
If aperture is wider than 1/4
11
:
( 1) Check that levels of incident and
reflected voltage inputs are with -
in rated lim i ts 0
(2) Check adjustment of tuning eye
circuit (see Adjustments) :
(3) Localize trouble in input cir-
cuit (see steps 2 to 7) 0
b
0
If tuning eye aperture is approxi-
mately 1/4
11
or smaller, localize
trouble i n circuit subsequent to
filters (steps 8 and 9)o
2
0
To localize trouble between the power
supply and instrument circu it, dis -
connect the 75 - volt , 210-volt, and
250-volt supplies from the instru -
ment circuit, terminate each with an
appropriate dummy load to ground,
and check the power supply, as de -
tailed below o
NOTE : Disconnect power cable or
turn power switch to off
position before changing any
connections.
a . 75-volt supply : unsolder the two jum -
pers from pin 5 of V21, and connect
pin 5 of V21 to ground through a
22, 000 -oh m 1-watt resistor
0
b .
210-volt supply : unsolder Rl2 l from
capacitor C66 , and connect Rl21 in
series with a 15, 000 - ohm 5-watt
resistor to ground. (Rl21 and C66
are identified in Fig. 21.)
c
0
250 - volt supply: at p in 3 of Vl9 , clip
jumper outgoing to capacitor C60
(Fig. 21). Connect pi n 3 of Vl9 to
ground through a 5, 000 - ohm 20~watt
resistor o
( 1)
If input voltages
are too low, in-
crease le vel at
external source.
(2) Readjust tuning
eye circuit, if
necessaryo