HP Lab Series - Page 43

Table
5-3.
Overall
Troubleshooting. (COntinued)
SYMPTOM
CHECKS
AND
PROBABLE
CAUSES
Poor
Stability
(Constant
Current)
b.
Noisy
programming
resistor
Rl6.
Continued
c.
CR5, CR34, C20, C3
leaky.
•
d.
Check
Rl8;,
Rl9,
R20,
R21, R54 for
noise
or
drift.
e.
Stage
Q2
defective.
Table
5-4.
High
Cutout
Voltage
Troubleshooting
STEP
ACTION
RESPONSE
PROBABLE
CAUSE
1
Check
turn
off
of
Q6
by
a.
Output
voltage
remains
high.
a.
06
shorted4
VR3
shorted..
shorting
Q4
emitter
to
b.
Output
voltage
decreases.
b.
Remove
short
and
proceed
collector.
to
~tep
2.
2
Check
turn
on
of
Q4
by
a.
Output
voltage
remains
high
•.
a.
Q4
open.
opening
the
emitter
of
b.
Output
voltage
decreases.
b.
Reconnect
lead
and
pro-
Q3.
ceed
to
Step
3.
3
Check
turn
off
of
Q3
by
a.
Output
voltage
remains
high.
a.
Q3
shorted'.
Ql7.defective.
disconnecting
collector
b.
Output
voltage
decreases.
b.
Q
lA
shorted.
Q 18
open.
lead
of
QlA,
Check
for
open
strap
be-
tween
A6
and
AS.
Check
RIO.for
open.
•
Table
5-5.
Low
Output
Voltage
Troubleshooting
STEP
ACTION
RESPONSE
PROBABLE
CAUSE
1
Check
turn
on
of
Q6
by·
a.
Output
voltage
remains.
low.
a.
Q6
open.
disconnecting
emitter
b.
Output
voltage
increases.
b.
Reconnect
emitter
lead
of
Q4.
and
proceed
to
Step
2.
2
Check
turn
off
of
Q4
by
a.
Output
voltage
remains
low.
a.
Q4
shorted.
Ql7
open.
shorting
Q3
emitter
to
Proceed
to
Step
4.
collector.
b.
Output
voltage
increases.
b.
Remove
short
and
proceed
to
Step
3.
3
Eliminate
constant
cur-
a.
Outpu.t
voltage
increases.
a.
Check
Q2B
for
open,
Q2A
rent
comj>arator
as
a
for
short.
Check
open
source
of
trouble
by
strap
between
A4
and
AS.
disconnecting
anode
of
Check
Rl6
for
short.
CR4.
b.
Output
voltage
r.emains low.
b.
Reconnect
lead
and
pro-
ceed
to
Step
4.
4
Check
turn
on
of
Q3
by
a.
Output
voltage
remains
low.
a.
Q3
open,
Ql7
open.
shorting
QlA
emitter
to
b.
Output
voltage
increases.
b.
Check
Q
lA
for
open,
QlB
collector."
for
short.
Check
for
open
strap
between
A6
and
A7
•
Check
RIO
for
short.
•
5-12