HP 3400A - Calibration and Power Supply Checks; Power Supply Checks; Low Frequency Calibration; Amplifier Offset Adjustment

Maintenance
Model
3400A
5-8
a.
Turn
instrument
power
off;
disconnect
input
signal
and
any
cable
connected
to
J2
(DC
OUT)
at
rear
of
instrument
and
allow
one
minute
for
meter
pointer
to
stabilize.
b.
Rotate
zero
adjust
CW
until
pointer
is
to
left
of
zero,
moving
up
scale.
Continue
until
pointer
is
at
zero.
If
pointer
overshoots
zero,
repeat
operation.
c.
When
the
pointer
is
exactly
at
zero,
rotate
the
adjusting
screw
slightly
counterclockwise
to
remove
tension
on
pointer
suspension.
If
the
meter
pointer
moves
to
the
left
during
this
adjustment,
repeat
steps
b
and
c.
5-19.
Power
Supply
Checks
5-20.
Power
supply
voltage
and
ac
ripple
tolerances
are
listed
in
Table
5-4.
Test
points
are
also
indicated
in
this
table.
When
making
ripple
voltage
measurements,
it
may
be
desirable
to
use
a
battery
powered
A.C.
Voltmeter
(H-P
403B)
to
avoid
any
undesirable
ground
loop
currents.
5-21.
Low
Frequency
Calibration
5-22.
Amplifier
Offset
Adjustment.
Do
the
following
a.
Perform
the
following
adjustment
only
for
Revision
C
A6
assemblies.
The
adjustment
is
not
required
for
Revision
A
assemblies.
b.
Remove
the
3400A’s
top
cover.
c.
Refer
to
the
Chopper
Amplifier
component
locator
(see
Page
6-7/6-8)
and
connect
TP5
to
TP1
(on
the
A6
assembly).
d.
Connect
a
DC
Voltmeter
between
TP6
and
TP1.
e.
Adjust
A6R629
(on
the
A6
assembly)
for
a
>2mV
dc
reading
on
the
dc
voltmeter.
5-23.
Amplifier
Gain
Adjustment.
Do
the
following
a.
Connect
test
setup
illustrated
in
Figure
5-1.
b.
Set
Model 3400A
RANGE
switch
to
0.01
volt
position.
c.
Adjust
the
Meter
Calibrator
for
a
0.01
V
400Hz
ac
volts
output;
set
the
Digital
Multimeter
to
measure
1V
dec.
d.
Remove
the
3400A’s
top
cover;
adjust
A6R627
(on
the
A6
assembly)
for
1.0V
as
in-
dicated
on
the
Digital
Multimeter.
e.
Adjust
R6
(FULL-SCALE
ADJUST)
for
Model
3400A
full-scale
meter
indication.
5-24.
1/10
Scale
Adjustment.
Do
the
following
a.
Connect
test
setup
illustrated
in
Figure
5-1;
omit
the
DC
Voltmeter.