HP 8340B Manual page 222

5-2.
10
MHz STANDARD ADJUSTMENT,
A51
(Cont'd)
NOTE
If front-panel red OVEN annunciator
is
lighted, do not make
internal
time
base adjustments. This annunciator lights when the oven for the
refer¬
ence crystal oscillator
is
not at operating temperature;
a
warm oven that
suddenly goes cold has lost power and requires service. Section
VIII
(Service) describes the action required
to repair
a
faulty oven.
1.
Connect equipment as shown in Figure 5-3 as follows:
a.
At
the OUT, disconnect jumper from rear-panel FREQUENCY STANDARD INT connector.
b.
Connect
oscilloscope
CH A
to the
DUT's FREQUENCY STANDARD INT connector.
(If the
oscilloscope being used does not have
a
50 Ohm
input,
connect Channel
A
through
a
50 Ohm
feedthrough.)
c.
Set
switch adjacent to the INT connector to INT position.
d.
Connect
a
frequency standard whose accuracy is
known
to be better than that of the internal
time base, such as an HP 5061A Cesium Beam,
to
the EXT TRIGGER
input of the
oscilloscope.
e.
Set LINE
switch to
ON.
2.
Set oscilloscope controls as
follows:
TIME/DIV
.....................................................
0.05 usec
CHAN A
VOLTS/DIV
.................................................
0.5
MAG
x
10 pushbutton
..........................................
OUT
DISPLAY A
pushbutton
................................................
IN
TRIGGER COMP A/B
......................................
. .
.
.,...,
A
INT/EXT
trigger
pushbutton
...... ......................................
IN
EXT Divide By
10
...................................................
OUT
SWEEP VERNIER
control
............................................
CAL
TRIGGER HOLDOFF
.................................
Fully
Counterclockwise
AC/DC
trigger pushbutton
........................................
OUT (AC)
POS/NEG
trigger pushbutton
....................................
OUT (POS)
Main
TRIGGER LEVEL
control
.....................................
Centered
3.
Adjust
Main
TRIGGER LEVEL
control as
necessary to
display sine
wave
signal on
oscilloscope.
4.
Remove dust cap screws used to seal the adjustments from
A51 10
MHz
Standard. Refer to
Figure 5-4 for location of
A51 10
MHz
Standard.
5.
Adjust A51 COARSE frequency
adjust for minimum sideways movement of the display signal.
Adjust A51 FINE frequency adjust for no sideways movement of display signal.
6.
Observe
the sine
wave signal
on
the oscilloscope for 100 seconds. The sine wave trace
should
move less than
1
cycle or
360
degrees.
7.
Disconnect oscilloscope and reinstall dust cover screws over
A51
adjustments. Reconnect rear
panel cable between
FREQUENCY STANDARD INT and EXT connectors.
5-16
Adjustments
HP 8340B/41B