HP 6177B Operating And Service Manual
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Table
5-10.
Troubleshooting
Constant
Current
Comparato:-
anc
Iviain
Erro,
!\r:1plifier-
I
STT'P
.cL.
ACnOr;
I
HESPONS::::
I
PROBAEL;-:
CAUSE
,
PI\RT
,
HIGH OUTPUT CURR;::J\T
h.
1
Check
operation
0:
Z 1
by
I
c.
Output
Cl..!rrent
cecreases.
I
c.
Zl
dsfective.
switching
Zl
and
Z2.
Output
current
high.
b,
Check
0191".
for-
~.
remE!lnS
open,
019B
:or
short,
02J
for
I
I
open,
VRIO
for
shor-t. CR3C
open
,
CR27, GR28
sr.ortec.
I
I
I
,
PART
B.
L010/
OUTPUT
CURREIC
1
I
Check
operation
of
Z 1
by
s\vitch-
a.
Output
current
increa
ses.
a.
Z1
defective.
ing
Zl
and
22.
):.
Output
current
remains
low.
b.
Check
Q19A
for
short
,
Q195
for
open,
021
Ior
short,
VR10
for
i
open,
5-48
REPAIR
AND
REPLACEMENT
to
free
adjustment
screw
from
meter
suspension.
If
pointer
moves,
repeat
steps
(b)
and
(c).
5-49
Wnen
replacing
a
defective
component,
reier
to
Section
VI
for
component
part
number
and
de-
scription.
Since
too
much
heat
could
lift
the
cop-
per
circuitry
off
of
a
printed
circuit
board,
a
iow
power
soldering
iron
(50 Vv'atts
maximum)
shoulc
be
used.
Solder
suckers
make
replacement
of
compo-
nents
easier
and
cleaner.
especially
when
multi-
lead
parts
are
being
used;
and
for
this
reason,
are
highly
recommended.
Use
only
high
quality
rosin
core
solder
when
repairing
printec
circuit
boards.
5-50
ADJUSTMENT
AND
CALIBRATION
5-51
Adjustment
and
calibration
may
be
required
after
performance
testing.
troubleshooting,
or
re-
pair
anc.
replacement.
If
more
than
one
adjustment
must
be
performed,
the
sequence
of
adjustments
presented
in
the
following
paragraphs
should
be
followed.
5-52
METER ZERO
5-53
Proceed
as
follows
to
mechanically
zero
the
meter:
a.
Turn
off
instrument
(after
it
has
reached
normal
operating
temperature)
and
allow
30
seconds
for
all
capacitors
to
discharge.
b.
Insert
sharp
pOinted
object
(pen
point
or
awl)
into
the
small
indentation
near
top
of
round
black
plastic
disc
located
directly
below
meter
face.
c.
Rotate
plastic
disc
clockwise
(cw)
until
meter
reads
zero,
then
rotate
CON
Slightly
in
order
5-14
5-54
AMMETER TRACKING
5-55
The
ammeter
circuit
is
adjusted
to
within
±2%,
(for
full
scale
readings)
at
the
factory
and
nonnally
does
not
require
adjustment
unless
a
component
in
the
meter
circuit
is
replaced.
5-56
To
calibrate
the
ammeter,
proceed
as
follows:
a,
Replace
any'
mete~
circuit
jumpers
(lor
2;
see
schematic)
that
have
been
removed
previously,
at
the
fa
ctOf'/.
b.
CODY1ect
test
·setup
of
Figure
5-3
(external
range
SWitch
and
medium-low
range
load
reSistors
can
be
eli::linated,
if
desired).
c.
Turn
VOLTAGE
control
fully
clockwise,
set
range
switch
to
highest
current
range,
and
connect
+
leae
of
differential
volt::leter
to
RS
1.
C.
Set
meter
switch
to
AMPS
and
adjust
CUR-
RENT
control
until
front
panel
meter
reads
exactly
the
maximurr,
rated
output
current.
e.
Observe
reading
on
differential
voltmeter.
If
it
is
between
0.981
and
1.019Vdc
(Model
6177B)
or
2.452
and
2.548Vdc
(Model
6181B)
leave
jumpers
1
and
2
connected
and
operate
normally.
f.
1£
differential
voltmeter
reading
is
be-
tween
0.941
and
O.981Vdc
(Model
6177B)
or
2.345
and
2.452Vdc
(Model
6181B)
remove
jumper
number
1
(across
R89).
Reading
should
now
be
within
nor-
mal
limits
of
step
(e).
g.
If
differential
voltmeter
reading
is
be-
tween
0.905
and
0.941Vdc
(Model 61778)
or
2.252
and
2.34
SVdc
(Model
6181B)
remove
jumper
number
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