HP Lab Series - Troubleshooting Procedures; Overall Troubleshooting Procedure; Reference Circuit Troubleshooting

CURRENT SAMPLING
TERMINALS
TO
UNGROUNDED
TO
GROUNDED
TERMINAL
OF
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TERMINAL
OF
POWER
SUPPLY
POWER
s·uPPL
y
Figure
5-9.
Output
Current
Measurement
Technique
POWER
SUPPLY
UNDER
TEST
CURRENT
SAMPLING
RESISTOR
Rx
MODEL NO.
62078
62098
DIFFERENTIAL
VOLTMETER
-+G
RESISTANCE
[OHMS)
Rx
I
Ry
7.5.n
I
793n.
15.n
I
31esa
Figure
5-10.
Output
Current,
Test
Setup
5-44
Current Output
and
Ammeter Accuracy.
Pro-
ceed
as
follows:
a.
Connect
test
setup
shown
in
Figure
5-10,
leaving
switch
Sl
open.
b.
Turn
CURRENT
controls
fully
clockwise.
c.
Set
METER
switch
to
highest
cUITent
range
and
turn
on
supply.
d.
Adjust
VOLTAGE
control
until
front
panel
meter
indicates
exactly
the
maximum
rated
output
current.
e.
Differential
voltmeter
should
read
l.5Vdc
:I:
45mVdc.
5-45
Load Regulation.
Definition: The
change,
.6IOUT.
in
the
static
value
of
de
output
current
result-
ing
from a
change
in
load
resistance
from
short
circuit
to
a
value
whl.ch
gives
max-
imum
rated
output
voltage
(or
vice
versa).
5-46
To
check
the
load
regulation,
proceed
as
fol-
lows:
a.
Connect
test
setup
shown
in
Figure
5-10.
b.
Turn
VOLTAGE
control
fully
clockwise.
c.
Set
METER
switch
to
highest
current
range
and
turn
on
supply.
5-8
d.
Adjust
CURRENT
controls
until
front panel
meter
reads
exactly
the
maXimum
rated
output
current.
·
e.
Read
and
record
voltage
indicated
on
dif-
ferential
voltmeter.
f.
Short
out
load
resistor
(Ry)
by
closing
•
switch
Sl.
g.
Reading
on
differential
voltmeter should
not vary from
reading
recorded
in
Step
(e) by more
than
34mVdi:::
for Model
6207B
and
66mVdc
for
62098.
5-47
Line
Regulation.
Definition:
The
change,
AioUT•
in
the
static
value
of
de
output
current
result-
ing
from a
change
in
ac
input
voltage
over
the
specified
range from
low
line
(10%
below
nominal}
to
high
line
(10%
above
nominal) or
from
high
line
to
low
line.
5-48
To
check
the
line
regulation,
proceed
as
fol-
lows:
a.
Utilize
test
setup
shown
in
Figure
5-10,
leaving
switch
Sl
open
throughout
test.
b.
Connect
variable
auto
transformer between
input
power
source
and
power
supply
power input.
c.
Adjust
auto
transformer
for
105Vac
input.
d.
Turn
VOLTAGE
control(s) fully
clockwise.
e.
Set
METER
switch
to
highest
cuITent range
and
turn
on
supply.
f. Adjust
CURRENT
controls
until front panel
meter
reads
exactly
the
maximum
rated
output
current.
g.
Read
and
record
voltage
indicated
on
dif-
•
ferential
voltmeter.
h.
Adjust
variable
auto
transformer
for 125Vac
input.
i.
Reading
on
differential
voltmeter should
not vary from
reading
recorded
in
Step
(g)
by more
than
34mVdc for 6207B
and
G"SmVdc
for 6209B.
5-49
Ripple
and
Noise.
Most
of
the
instructions
pertaining
to
the
ground loop
and
pickup
problems
associated
with
constant
voltage
ripple
and
noise
measurement
also
apply
to
the
measurement
of
con-
stant
current
ripple
and
noise.
Figure
5-11
illus-
trates
the
most
important
precautions
to
be
observed
when
measuring
the
ripple
and
noise
of
a
constant
current
supply.
The
presence
of
a 120Hz waveform
on
the
oscilloscope
is
normally
indicative
of a
correct
measurement
method. A
waveshape
having
60Hz
as
its
fundamental
component
is
typically
associated
with
an
incorrect
measurement
setup.
5-50
Ripple
and
Noise
Measurement. To
check
the
ripple
and
noise,
proceed
as
follows:
a.
Connect
the
oscilloscope
or
RMS
voltmeter
as
shown
in
Figures
5-llB
or
5-llC.
b.
Rotate
the
VOLTAGE
controls
fully
clock-
wise.
c.
Turn
on
supply
and
adjust
CURRENT
con-
trols
until
front
panel
meter
reads
exactly
the
maxi- •
mum
rated
output
current.
_