Power Supply Checks; Low Frequency Calibration; 1/10 Scale Adjustment; 1 Volt Adjustment - HP 3400A Operating And Service Manual

Model 3400A
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 indi-
cated
in this table.
When
making
ripple voltage
measurements,
it
may
be desirable
to
use
a bat-
tery
powered
A. C.
Voltmeter (H-P 403B)
to avoid
any undesirable ground
loop currents.
5-21.
LOW
FREQUENCY
CALIBRATION.
5-22.
AMPLIFIER
GAIN
ADJUSTMENT.
a.
Connect
test
setup illustrated in
Figure 5-1.
b.
Set
Model
3400
A RANGE
switch
to
0.
01 volt
position.
c.
Adjust Voltmeter Calibrator
for
0.
01
volt
rms,
400
Hz
output; set
DC
Voltmeter
to
read
1.
0.
d.
Remove Model 3400A
top cover; adjust
R4
(CAL)
for
1.
volt
as indicated on
DC
Volt-
meter.
If
R4 (CAL)
does
not
have enough
range to calibrate the dc output, the value
of
R3 should be changed.
The
range
of
R3
is
from
820
ohms
to
2.
16
k ohms.
e.
Adjust
R6 (FULL-SCALE ADJUST)
for
Model
3400A
full-
scale
meter
indication.
Section
V
5-23.
1/10
SCALE ADJUSTMENT.
a.
b.
Connect
test setup illustrated
in
Figure 5-1;
omit
the
DC
Voltmeter.
Set
Model 3400A
RANGE
switch
to 0.
1
volt
position
and adjust Voltmeter
Calibrator for
0.
01 volt
rms, 400
Hz
output.
NOTE-
The
1/10
SCALE ADJUST
should
be
set slightly
low
(needle's width)
to
reduce
meter
(needle) offset
with shorted
input.
c.
Adjust
R7
(1/10
SCALE
ADJUST)
for Model
3400A
1/10 scale
meter
indication.
Change
value
of
R8
if it
is
necessary
to
increase
the
adjustment range
of
R7.
The
range
of
R8
is
from approximately 270
ohms
to
430
ohms.
See Table 5-7.
5-24.
1
VOLT ADJUSTMENT.
a.
Connect
test setup
illustrated
in
Figure
5-1;
omit
the
DC
Voltmeter.
b.
Set
Model 3400A
RANGE
switch
to 1
volt
position.
c.
Adjust voltmeter
calibrator for
1.
volt
rms,
400
Hz
output.
d.
Remove
right side
cover
(INPUT
side)
and
adjust
R104
(1
V ADJUST)
for
Model 3400A
full-scale
meter
indication.
Table 5-4.
Power
Supply
Checks
•
POWER
SUPPLY
TEST EQUIPMENT
AND
CHECK
POINT
DC
VOLTAGE
SPECIFICATIONS
REGULATION
(Vary Line Voltage
Between
103.
5
and
126. 5 vac)
RIPPLE
SPECIFICATIONS
-17.5
Vdc Connect
DC
Voltmeter,
AC
Voltmeter, or
Os-
cilloscope
between
violet
lead on video
amplifier (A4)
board
and
chassis ground.
-16. 8 to
18.2
Vdc
±0.
5 volt
from nominal
reading
at
115
Vac
line.
400
/J.V
rms
or
1.
1
mV
p-p
h-75
Vdc Connect
DC
Voltmeter,
AC
Voltmeter, or Oscil-
loscope
between red/wht/
blue on video amplifier
A4
and chassis ground.
70.0
to
78.0 Vdc ±
1
volt
from nominal
reading
at
115
Vac
line.
400
/iV
rms
or
1. 1
mV
p-p
-6. 3
Vdc
Connect
DC
Voltmeter,
AC
Voltmeter, or Oscil-
loscope
between
Q3
emitter (grey
lead)
and
chassis ground.
-5. 9 to
-6.
5
Vdc
±0.
1
volt
from nominal
reading
at
115
Vac
line.
750
(iV
rms
or
2.
mV
p-p
5-5