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Section IV
Paragraphs 4-45 to 4-61
cable to the floating collar on the spring loaded idler
shaft with 4-40 x 1/4 inch round- head machine screw.
g. Wind two full turns of the drive cable onto the
floating collar.
Be sure the spring load nut is posi-
tioned so that one of the setscrews is accessible.
Place a 9/16 inch open-end wrench over the spring
load nut to prevent its turning.
h. Wrap one and a half turns of the drive cable
around
the
drive pulley as shown in figure 4-6.
i. Rotate the spring- loaded idler shaft so that the
number 4-40 screw hole in the spring- loading collar
is accessible.
j. Attach the long end of drive cable to the spring
loading
collar
using
the
4-40
x 1/4 round- head
machine screw.
k. Place a screwdriver in the slot at end of the
spring- loaded idler shaft and rotate shaft counter-
clockwise to remove slack in drive cable. Continue
to hold spring- load nut with end wrench.
m. Tighten one setscrew in the spring- load nut and
remove end wrench.
n. Turn frequency dial to approximately mid- range
and seat cable in the slot on the drive pulley.
p. Holding spring- load nut with 9/16 inch open-end
wrench, loosen the previously tightened setscrew in
spring- load nut and turn spring- loaded idler shaft
counterclockwise to a torque of approximately 7 inch-
pounds.
Retighten setscrew and remove wrench.
q. Hold frequency dial against its low frequency
stop.
Slip the drive cable on the drive pulley by
turning the spring- loaded idler shaft with screw-
driver.
Turn the idler shaft until both tuning capa-
citors are fully meshed.
r. Tighten the 4-40 allen setscrew in drive pulley.
s. Rotate frequency dial through its range and ob-
serve position of drive cable.
t. Check dial calibration as outlined in para. 4-16.
u. Replace aluminum shielding plate between the
rf oscillator and rf amplifier.
v. Turn
instrument
right- side
up.
Replace rf
generator shield and cabinet.
This completes the
procedure.
4-56. PERFORMANCE CHECK.
4-57. The following procedures check performance
and
verify
proper
operation
of the Model
606A,
4-58. FREQUENCY CALIBRATION.
a. Set line voltage to 115 volts.
b. Perform operations listed in paragraph 4-17.
c. Repeat this procedure with line voltage set at
102.5 volts and 127.5 volts.
4-14
Model 606A
4-59. OUTPUT.
a. With line voltage set at 115 volts perform oper-
ations indicated in paragraph 4-18.
b. Rotate output meter RANGE switch through each
position,
adjusting output control at each setting.
Output should be adjustable from zero to full scale
in each position of the range switch.
c. Repeat steps a and b with line voltage set at
102.5 volts and 127.5 volts.
d. To
check output impedance switch VTVM to
3 volt range.
e. Adjust Model 606A output to read
1 volt on
VTVM at 20 mc.
f. Remove the 50 ohm load. Output voltage should
rise to 2 volts ± 0.1 volt.
g. Set Model 606A FREQUENCY dial to 65 mc and
reconnect the 50 ohm load.
h. Reset output to 1 volt as indicated by VTVM.
i. Remove 50 ohm load.
Output should rise to 2
volts ± 0.2 volt.
4-60. MODULATION.
a. Perform procedure outlined in paragraph 4-15
with line voltage set at 115 volts.
b. Rotate FREQUENCY dial through all
ranges;
observe envelope pattern for distortion and squegging.
c. Repeat steps a and b with line voltage set at
102.5 volts and 127.5 volts.
d. Reset line voltage to 115 volts.
e. To check external modulation set MODULATION
SELECTOR to EXT.AC.
f. Turn MODULATION AMPLITUDE control fully
clockwise.
g. Set FREQUENCY control to 15 mc.
h. Connect an audio oscillator ( 20 cps to 20 kc) to
MODULATION input jack of Model 606A and SYNC in-
put of oscilloscope.
i. Adjust the audio oscillator to produce a signal
of 4.5 volts peak.
PERCENT MODULATION meter
of Model 606A should indicate at least 100%.
j. Repeat steps e to i with line voltage set at 102.5
volts and 127.5 volts.
4-61. FREQUENCY DRIFT.
a. Allow
Model
606A to warm up for at least
one hour.
b. Set FREQUENCY control to 1 mc.
c. Monitor output of Model 606A with a counter for
10 minutes.
Frequency drift should be less than 50
cycles over the 10 minute period.
00170-2
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Table of Contents
Troubleshooting
