Table of Contents
Advertisement
Model 5065A
Circuit Diagrams, Theory, and Maintenance
j.
Disconnect the +20-volt red lead from the A3
Multiplier Assembly.
k.
Set
3581A AMPLITUDE REFERENCE control
to X.001. Noise reading should be in mid or lower half of
scale. Meter should not peg on noise peaks. Adjust INPUT
SENSITIVITY if necessary to achieve this. OVERLOAD
light should remain out.
I.
3581A reading will be noisy. Watch meter for
about 20 seconds to estimate the average reading. Record
this reading as V
n
. Typical value is approximately 300 /iV.
m.
Multiply this reading by 0.72 and divide into V
s
measured in step i. Note: the .72 factor converts the noise
measured in the 3581A's 10 Hz resolution bandwidth
(11.5 Hz noise bandwidth) to equivalent noise in a 6 Hz
noise bandwidth. If another analyzer is used its noise
measurement must be converted by use of the formula
where B = the noise bandwidth of the analyzer used for
the measurement, and V is the measured noise voltage.
Signal-to-noise ratio is given by
.72 X V
n
For satisfactory operation, the signal-to-noise ratio should
be 250 or greater. Low signal-to-noise ratio can be caused
by improper alignment of the RF matching network in the
A3 Multiplier Assembly or insufficient 137 Hz phase mod
ulation (see step f of Section 5-25, RF Alignment, the pre
ceding section).
n. Reconnect +20V red lead to the A3 Multiplier
Assembly. Set OSC FREQ ADJ FINE Control at 250.
5-27. Modulation Frequency Adjustment
a. Connect a frequency counter to A8TP2 and
measure the frequency.
If the frequency is between
136 Hz and 138 Hz do not make any adjustments.
b.
If frequency of step a is outside 137 Hz +1 Hz
range, adjust A8R8 for a frequency of 137 Hz ±1 Hz.
5-28. Phase Adjustment Recheck
a.
Before proceeding further, locate the resonance
signal and set up a frequency offset as described in
Section 5-24, Frequency Adjustments.
b.
If the oscilloscope pattern is split (out of
phase)
readjust A8R43 until the pattern looks like
Figure 5-10.
c.
Remove oscilloscope connections.
5-29. Phase Detector and Integrator Zero Adjustment
a. Set FUNCTION switch to LOOP OPEN.
b. Disconnect yellow lead (slide-on connector)
from A7 AC Amplifier.
c.
Connect a dc voltmeter to A8TP3, and adjust
A8R35 for a reading of less than 1 mV dc.
d.
Disconnect dc voltmeter from A8TP3 and con-
v .
nect it to CONTROL jack on the rear panel.
e. Connect a short jumper between pins 14 and 15
—
on A9 Assembly socket (XA9) to short the A9 input.
f. Set FUNCTION switch to OPER and measure
dc voltage at the rear panel CONTROL jack.
—
g.
The voltage of the previous step will probably
be drifting slightly. Adjust A9 Integrator zero
control
R10 (FINE) to stop this drift. If R10 does not have suf-
_
ficient range to stop the drift, then R3 (COARSE)
should be adjusted to bring R10 into range. To use the
dc voltmeter on a lower range for finer adjustment, set
FUNCTION switch to LOOP OPEN and then back to
—
OPER.
This will discharge the integrating capacitor
and set the control voltage near zero.
Observe the
control voltage for a short period of time.
If the drift
exceeds 20 mV/minute, repeat the zeroing adjustments.
~
h.
Remove shorting jumper from XA9 (14 and 15).
Reconnect the yellow wire slide-on connector to A7.
Dc voltmeter may be left connected for the next step.
—
5-30. Loop Gain Adjustment
a.
Check that the dc voltmeter is connected to
—
rear-panel CONTROL jack and that controls are set
as follows:
FUNCTION
OPER
_
OSC FREQ ADJ FINE
250
b. Observing the dc voltmeter, adjust OSC FREQ
ADJ COARSE for less than 100 mV at the CONTROL
—
jack.
c. Set FUNCTION switch to LOOP OPEN and
connect the dc voltmeter to A8TP3.
d.
Set OSC FREQ ADJ FINE to 200 and then adjust
A7R17 for a reading of +0.5 ±.05 volts on the dc voltmeter.
e. Adjust OSC FREQ ADJ FINE to 300.
Dc volt-
"~
meter should read approximately -.5 volts.
If the
reading is off appreciably,
repeat this
procedure.
f.
Set OSC FREQ ADJ FINE at 250 and remove
the dc voltmeter connections.
5-31. Logic Assembly (A14) Alignment
a.
Remove the A14 Logic Assembly circuit board
and mount it on the extender board provided. It is not
necessary to remove power when removing this board.
b. Set front-panel controls as follows:
FUNCTION
OPER
OSC FREQ ADJ FINE
250
CIRCUIT CHECK switch .. 2ND HARMONIC
5-14
Advertisement
Table of Contents
