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Model 5065A
Circuit Diagrams, Theory, and Maintenance
5-19. LOOP ALIGNMENT PROCEDURE
5-20. Introduction
5-21.
If any loop adjustment has been changed, the
frequency stabilizing loop of the 5065A should be re
aligned according to the procedures of the following
sections. Allow at least 3 hours warmup to permit all
circuits to become fully stabilized before proceeding
with this alignment.
The loop adjustments are as
follows:
5-22. +20 Volt Adjustment (A15 Power Supply and
Regulator Assembly)
5-23.
With power disconnected, remove A15 Power
Supply circuit board. Mount it on an extender board.
Connect power, and after a few minutes warmup,
monitor +20 volts at A15C5. Adjust A15R17 as neces
sary. Be sure to disconnect line power before replacing
the A15 Power Supply circuit board.
5-24. A10 Frequency Adjustment
a. Set controls: FUNCTION switch at LOOP OPEN
OSC FREQ ADJ FINE at 250.
b.
Connect oscilloscope vertical input to A8TP3.
Connect oscilloscope horizontal input to the sweep test
output A8TP2. Set horizontal gain for about a 5 cm
horizontal sweep. Set vertical gain at about .05 volts/cm
through a 10:1 divider probe.
c. Adjust A3R3, A3R11 full ccw then cw % turn.
Using a screwdriver, adjust front-panel OSC FREQ ADJ
COARSE slowly until an oscilloscope pattern roughly
similar to Figure 5-8 appears. This oscilloscope response
is an indication that the 5065A is turned near resonance.
Figure 5-8. Waveform at A8TP3 with Severe
Phase Shift
5-25. RFAlignment-
a.
Remove bottom cover for access to chassis
bottom. Remove A5 Assembly if Option 001 is installed
for access to the multiplier adjustments.
Note that
removal of the A5 Assembly in no way affects operation
of the rest of the 5065A circuits.
b.
Figure 5-9 shows the RF alignment test equip
ment setup.
c.
Before proceeding locate the resonance signal
and set up a frequency offset as described in Para
graph 5-24.
Figure 5-9. R.F. Alignment Setup
HPI8CA
OSCILLOSCOPE
HORIZ INPUT
A 8 T P 2
VERT INPUT
A 8 T P 3
H P 5 0 6 5 A
RU8IDIUM
VAPOR
FREQUENCY
STANDARD
H P 4 I 0 C
DC
VOLTMETER
A 3 T P 2
GRD
d.
Adjust A3R3 on the Multiplier Assembly for
maximum amplitude of the oscilloscope signal.
Then
adjust
A3R3
ccw
until
the
oscilloscope
pattern
amplitude is reduced by Vz to prevent RVFR and
amplifier saturation during this alighnment.
Figure 5-10. Oscilloscope Indication at Resonance
with A8R43 iModulating Phase Adjustmenti
correctly adjusted
d.
Note that when A10 Oscillator is adjusted
through resonance, the oscilloscope pattern will change
from a positive hump to a straight line (which is the
resonance center); and then to a negative hump.
Ad
just OSC FREQ ADJ COARSE for the straight line
center-resonance position between the positive and
negative humps.
e. Set OSC FREQ ADJ FINE at 200 for a 50 x 10-'°
frequency offset.
An oscilloscope pattern similar to
Figure 5-8 or 5-10 will appear.
f.
Make a preliminary phase adjustment if neces
sary. Adjust A8R43 (on top of A8 board) so the ends
of the waveform come together as shown in Figure 5-10.
e.
Adjust A8R43 ladjustment facing top of A8
board | for minimum phase shift on the wave form. A pat
tern without phase shift is shown in Figure 5-10. Phase
shift will split the pattern at the two ends as in Figure 5-8.
f.
Phase modulation adjustment.
Adjust A3R11
cw until the oscilloscope pattern just reaches a maxi
mum, then adjust A3R11 slightly ccw so the pattern is
reduced by 5 or 10%.
NOTE
It may be necessary to readjust A8R43 for
minimum phase shift.
5-12
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