HP 6296A - Page 41

Table
5-6.
Common
Troubles
Symptom
Checks
and
Probable
Causes
a.
Check
operating
setup
for
ground
loops,
b.
If
output
floating,
connect
1
µ.f
capacitor
between
output
and
ground
•
c.
Ensure
that
supply
is
not
crossing
over
to
constant
current
mode
High
ripple
under
loaded
conditions.
d.
Check
for low
voltage
across
CSOO
or
Q400.
e.
Check
for
excessive
ripple
on
reference
voltages.
Peak-to-peak
ripple
should
be
less
than
2mV
for +9.
4V
and
-6.
2V
and
less
than
4mV
for +15.
4V.
Poor
line
regulation
a.
Check
reference
circuit
(Paragraph
5-31).
a.
Measurement
technique.
(Paragraph
5-16.)
Poor
load
regulation
b.
Check
reference
circuit
(Paragraph
5-31).
(Constant
Voltage)
c.
Ensure
that
supply
is
not
going
into
current
limit.
Check
consta.nt
current
input
circuit.
a.
Check
reference
circuit
(Paragraph
5-31).
Poor
load
regulation
b.
C802,
C803,
and
CR809
leaky,
(Constant
Current)
c.
Ensure
that
supply
is
not
crossing
over
to
constant
voltage
opera-
tion.
Check
constant
voltage
input
circuit.
Oscillates
(Constant
Check
C301
for
open,
adjustment
of
R307
(Paragraph
5-50).
Voltage
I
Constant
a.
Current)
b.
Check
Rl03, ClOO
or
R304,
C300.
a.
Check
reference
voltages
(Paragraph
5-31).
Poor
Stability
b.
Noisy
programming
resistors
R813, R814.
c.
CR100, CRlOl
leaky.
(Constant
Voltage)
d.
Check
Rl04, R805, R806,
CS 0
l for
noise
or
drift.
..
e •
Stage
QlOO
defective.
•
a.
Check
reference
voltages
(Paragraph
5-31).
Poor
Stability
b.
Noisy
programming
resistors
R809,
R81
o.
c.
CR809, C803,
C802
leaky.
(Constant
Current)
d.
Check
R807, R808, R200, R800,
for
noise
or
drift.
e.
Stage
Q200
defective.
Table
5-7.
Selected
Semiconductor
Characteristics
Reference
Characteristics
~
Stock
No.
Suggested
Designator
Replacement
Matched
differential
ampli-
fier.
NPN Si
Planar.
70
(min.)
1854-0229
QlOO,
Q200
hFE
IC=
1
mA.
VcE
=
5V.
2N2917 G.
E.
Ico 0.01
µ.a
@Vcbo
=
SV.
Q303.
Q400
NPN
power.
hFE
=
35 (min);
1854-0225
2N3055
R.
C.
A.
(Q401)
@
le
=
4A.
VcE
=
4V.
Q851
Matched
differential
amplifier.
1854-0221
2N4045
Union
Carbide
NPN
Si.
•
5-10