Low Output Voltage Troubleshooting - HP BENCH Series Operating And Service Manual

Table 5-3. Reference, Bias, and Filtered DC Troubleshooting
METER
COMMON
METER
POSITIVE
NORMAL
VDC
NORMAL
RIPPLE (P-P)
PROBABLE
CAUSE
C5(-) C5(+)
+48 ± 4.8V
2V
T1,C10,CR10,CR11,C5
+ S
7
+ 12.4 ± 0.6V
0. 5niV
VR4,Q11,VR7
+ S 8
+ 6.2 ± 0.3V
0.2mV
VR6.R25
9
+S
+ 6.2 ± 0.3V
0. ImV
VR3,Q9,R30,VR8
11
+S + 12.4 ± 0.6V
4. 5mV
VR1,R27,R30
-OUT
6
22 ± 2.2V (6213A)
44 ± 4.5V (6215A)
78 ± 7.8V (6217A)
3V
400mV
500mV
CR15,CR16, C9,R32,T1
Table 5-4. Low Output Voltage Troubleshooting
STEP ACTION
RESPONSE
PROBABLE CAUSE
1
Turn the VOLTAGE control fully-
clockwise and disconnect the
load
2 To eliminate the current limit
circuit as a cause of the mal
function, remove CR4 cathode or
anode lead
a. Output increases
b. Output remains
low
a. CR4 or Q3 defective
b. Reconnect CR4 and proceed
to Step 3
3
Check conduction of Q7 by con
necting a jumper between Q5
emitter and base
a. Output remains
low
b. Output increases
a. Q7, CR7, or associated parts
defective
b. Remove jumper and proceed
to Step 4
4
Check turnoff of Q5 by shorting
Q4 emitter to collector
a. Output remains
low
b. Output increases
a. Q5, R19, R20 defective
b. Remove jumper and proceed
to Step 5
5
Check conduction of Q4 by
shorting Q1 emitter to collector
a. Output remains
low
b. Output increases
a. Stage Q4 defective
b. Stage Q1/Q2 defective.
Check R10,R11,C1 for short
and R12 for open.
5-10