HP 416A - Trouble Shooting; Instrument Not Operating

416A004 ~ 1 10/26 /5 5 Se rial 79 and above
Trouble Shooting - -
The following information i s des i gned to aid in trouble shooting a defect iv e i nstrument :
Symptoms
Instrument NOT
operatin g; in d ic ator
lamp NOT on .
Instrument NOT
operat i ng ; i ndic -
1 a tor lamp ON .
(JI
00
I
Possible Cause
Fuse F 1 open due to
defecti v e fuse or
ov erload in power
supply .
HV regulator not
funct i oning ,
Test Procedure
Replace fuse F 1; if it blows again it
indi cates :
1. Defect ive recti fier tube Vl8 .
2 .
Short circuit in winding associated
with transformer T 1.
3 .
Short circuit in filament wi ring .
4 .
Defective transformer T 1.
5 .
Defective rectifier SRI.
6 . Short circuit in DC wiring.
1. Connect VTVM to pin 3 of Vl9 and
check regulator output (see Adjust -
ment of HV Regulator) . If regulator
output is 0 or cannot be brought up
to 250 volts by adjustment of R 116 :
a .
Check v oltage from pin 8 of VIS
to ground; should measure 410 volts
±10 volts.
( 1) If 410 volts ±10 volts not pre-
sent at rectifier Vl8 output ,
check for defective Vl8 or short
in T 1 secondary winding.
(2) If Vl8 output is at correct level;
b . Check voltage from pin 5 of Vl9 to
ground; should measure 10 volts
less than measurement taken at
pin 8 of Vl8.
( 1) If there is no voltage , prob-
ably coil L3 is open.
(2) If voltage drop across LC
filter is much greater than 10
volts , check capacitor C66 .
Remedies
1. Replace Vl8.
2 . Locate and clear
short circuit .
3 .
Locate and clear
short circuit .
4. Replace transformer .
5. Replace rectifier SRl.
6. Locate and replace
defective component .
( 1)
If Vl8 defecti ve,
replace ; if Vl8
good, locate and
clear T 1 short.
b.
( 1) If L3 is defecti ve,
replace.
(2) If after accurate
tests C66 is
found defecti ve,
replace.