HP 416A - Page 79

!
O"
I-'
I
Symptoms
Instrument op er -
atingbut meter
indicator action is
unstable or erratic
(cont ' d) .
Possible Cause
Insufficient voltage
at inputs (cont
1
d) .
Trouble in power
supply .
Trouble on 210 -
v
olt bus .
Trouble on 250-
volt or 7 5 - volt
bus .
Trouble in instru -
ment.
Test Procedure
2. c . (cont ' d)
NOTE : When reconnecting the C60
jumper , it may be soldered to
pin 2 (instead of pin 3) of Vl9.
d. Check the power supply output level
and line regulation as described under
Adjustments .
( 1)
If rated output and/or regulation
are not obtained , trouble probably
is in the power supply circuit.
Check as described abo v e under
"HV regulator not functioning" .
(2 ) If rated output and regulation are
obtained trouble is in instrument
circuits . Suggested localization
procedures are given in steps 3 to
8, It is recommended that local -
ization be performed in the order
given in this chart .
3 . Reconnect the 210-volt supply (connect
Rl2 l to capacitor C66 [erminal to
which is connected jumper outgoing to
Rl8 and RB2] ). Again check power supply
output level and line regulation.
a . If 250 - volt output and regulation are not
obtained , turn off the power switch ,
and check the 210-volt bus with an ohm-
meter for a possible short to ground.
b. If output and regulation are obtained:
4 . Disconnect the 210 - volt supply , and re-
connect the 75-volt and 250-volt sup-
plies . Again check power supply out-
put level and line regulation . If 250-
vo lt output an d regulation are not ob -
tained , turn off the power switch , and
check the 2 50 -vo lt bus and the 7 5 -volt
bus , with an ohmmeter for a possible
short to groun d .
5 .
Set up test procedure as described un -
der Adjustments and shown i n Fig. 18,
and measure voltage levels at input to
aAoqB pm:.? 6l Bn.ras SS/9.'Z/OI I -;- f700V9If7
Remedies
a. Loc ate and cle a r
short.
a. Locate and c lea.r
short.