10 Mhz Standard Adjustment, Asi - HP 8340B Manual

5-2. 10 MHz STANDARD ADJUSTMENT, ASI (Cont'd)
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 NT connector.
b. Connect oscilloscope CH A to the OUT'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 NT 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
CHAN A VOLTS/DIV
MAG x 10 pushbutton
DISPLAY A pushbutton
TRIGGER COMP A/B
NT/EXT trigger pushbutton
EXT Divide By 10
SWEEP VERNIER control
TRIGGER HOLDOFF
AC/DC trigger pushbutton
POS/NEG trigger pushbutton
Main TRIGGER LEVEL control
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 ASi 10 MHz Standard. Refer to
Figure 5-4 for location of ASi 10 MHz Standard.
5. Adjust ASi COARSE frequency adjust for minimum sideways movement of the display signal.
Adjust ASi 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 ASi adjustments. Reconnect rear
panel cable between FREQUENCY STANDARD INT and EXT connectors.
5-16 Adjustments
NOTE
0.05 jisec
0.5
OUT
IN
A
IN
OUT
CAL
Fully Counterclockwise
OUT (AC)
OUT (POS)
Centered
HP 8340B/41B