HP 654A - Frequency Calibration Test Setup

Section V
5-49.During calibration, the instrument bottom cover is
removed; the top cover is removed to make adjustments
and replaced while making frequency measurements ( not
necessary to replace retaining screws), all internal shields
must be in place and held firmly by retaining screws. If
desired Figure 5-17 gives a scaled drawing of top and
bottom alignment access covers with cut-outs that will
allow adjustments while the covers are in place. The
dimensions are given in inches.
5-50. FEEDBACK LEVEL ADJUSTMENT.
a. Connect the equipment shown in Figure 5-15.
b. Set the 654A controls as follows:
FREQUENCY dial extreme clockwise
FREQUENCY RANGE X1K
OUTPUT LEVEL dBm + 10,0
AMPLITUDE extreme counter- clockwise
IMPEDANCE 50 UNBAL
NOTE
Adjust A2C1, S2C2, and S2C8, if
necessary, to start oscillations.
c. Adjust A2R3 ( Feedback Level Adj.) for an
indication on the dc voltmeter of - 350mV,
+/-10mV.
d. For oscillator troubleshooting, refer to Paragraph
5-81.
5-51. DISTORTION ADJUSTMENT.
a. Connect the 654A to the distortion analyzer as
shown in Figure 5-10. Set the 654A controls for a
frequency of 1 X 100.
b. Adjust A2R4 ( Distortion Adj.) for minimum
distortion, which should be at least 46dB. If the
tolerance cannot be met, change the value of
A2R9*
Model 654A
c. Check distortion at other dial and range settings.
NOTE
You can adjust A 1 R4 at other frequency
to get them into specification providing
that you still are in specification at 1 X
100.
d. Disconnect the distortion analyzer.
5-52. Frequency Dial and 1 K Range Adjustment.
a. Preliminary mechanical adjustments ( perform only
if necessary).
1) To prevent gear backlash problems during
alignment, make sure that there is no move-
ment between MP1 and MP2. See Figure 6-1.
(They must be pressed tightly together.) Also
MP3, 4, and MPS spring gear assembly must be
under tension.
2) Check to make sure that the stop MP6 prevents
the tuning capacitor from being completely
closed. MP6 should hold the capacitor at least
1/16 inch open. Adjust if necessary.
3) With the dial set to maximum clockwise posi-
tion, slip the dial face such that the first eark-
left of 1 is 1/16 inch to the right of the fixed
indicator. To slip dial, remove Frequency dial
knob and loosen 4 dial retaining screws. After
slipping dial, retighten the screws.
b. Connect equipment as shown in Figure 5-15 and
set the 654A controls as in Paragraph 5-50b.
Record output frequency.
c. Record frequency at dial settings 1, 2, 5, 8 and 10.
If some readings are high and some are low,
proceed to step e. If all readings are high or all
TEST OSCILLATOR
hp654A
654A- II- 1901
TO
A2TP2
COUNTER OUTPUT
(REAR PANEL)
VOLTMETER
hp 427A
ELECTRONIC COUNTER
hp 5245L
Figure 5-15. Frequency Calibration Test Setup
5-14