HP 6268B Operating And Service Manual

Table 5-5. Series Regulator Troubleshooting. High Output Voltage (Continued)
STEP
ACTION
RESPONSE
PROBABLE CAUSE
1
Check turn-on of error amplifier
Q42 by momentarily shorting
base (TP44) to collector (TP68).
a. Output voltage remains
high.
b. Output voltage decreases.
a. Q42 open.
b. Proceed to step 5.
5
Check turn-off of mixer amplifier
Q41 by momentarily shorting
base (TP40) to emitter (TP47).
a. Output voltage
remains high.
b. Output voltage decreases.
a. Q41 shorted.
b. Proceed to step 6.
6
Measure the voltage at pin 1 of
constant-voltage comparator Z1
(between TP11 and the +S
sensing terminal).
a. TP11 voltage is about
+0.7 volts.
b. TP11 voltage is about
-0.7 volts.
a. Open sensing lead, open strap between
A1 and A2, A5R121 or A5R122 open.
b. CR1 open, Z1 or Z2 defective.
Table 5-6. Series Regulator Troubleshooting, Low Output Voltage
STEP
ACTION
RESPONSE
PROBABLE CAUSE
1
Make these tests with external sour
control set
Check turn-off of error amplifier
A4Q101 by momentarily short¬
ing base (TP45) to emitter
(TP100).
ce connected as described in ste
to the center of its range while
a. Output voltage remains
low.
b. Output voltage rises.
p 3 of Table 5-4. Leave the coarse voltage
making these tests.
a. A4Q101 shorted; A4Q102 open, thermal
switch A4TS101 open; A4Q103 through
A4Q106, A40108, or A4Q110 open;
A4R1 50 through A4R165 (as applicable)
open; A4CR106 (or A4CR107) shorted.
b. Proceed to step 2.
2
Check turn-off of error amplifier
Q42 by momentarily shorting
base (TP44) to emitter (TP46).
a. Output voltage remains
low.
b. Output voltage rises.
a. Q42 shorted, CR44 shorted.
b. Proceed to step 3.
3
Isolate fault to constant-voltage
comparator or constant-current
comparator by opening the
cathode of CR20.
a. Output voltage rises.
b. Output voltage remains
low.
a. Z1 defective, open strap between A6 and
A7, or shorted A5R123 or A5R124.
b. Reconnect CR20 and proceed to step 4.
1
Check turn-on of mixer amplifier
Q41 by momentarily shorting
base (TP40) to collector (TP41).
a. Output voltage remains
low.
b. Output voltage rises.
a. Q41, CR40, or CR41 open; Q40 shorted.
b. Proceed to step 5.
5
Measure the voltage at pin 1 of
constant-voltage comparator Z1
(between TP1 land the+S
sensing terminal).
a. TP11 voltage is about
—0.7 volts.
b. TP11 voltage is about
+0.7 volts.
a. Open strap between A2 and A3; CR3, CR7,
or Q1 shorted; VR1, R3, R4, or R5 open.
b. CR1, CR4, Z1 or Z2 defective.
5-1 2

HP 6268B Specifications

General

Brand	HP
Model	6268B
Category	Power Supply
Language	English