Section VI
Paragraphs 6-1 to 6-2
SECTION VI
TROUBLE SHOOTING AND CORRECTION
oscilloscope or a-c vacuum tube voltmeter connected
6-1. SECTION ISOLATION.
to the AUDIO OUT jack. These audio signals are
6-2. It is possible to detect many troubles in Signal
obtained by demodulating the r-f signal which appears
Generator SG-13/ARN without removing the instru-
across the final tank circuit and therefore provide a
ment from its case. The carrier level is indicated
check on the entire modulation process as well as on
on the meter with the METER switch in the CAR
the audio section. The following chart lists probable
position. It gives evidence of proper operation of the
trouble symptoms with causes and remedies.
r-f section. Audio signals can be observed with an
SYMPTOM
PROBABLE CAUSE
REMEDY
Attenuator stop set incorrectly
See Section VIII paragraph
CARRIER meter suddenly
drops to zero as MICRO-
VOLTS dial is turned to
maximum posit ion
1. Sticking slug rack
Lubricate, See Section IV
R-f output on CARRIER
meter varies depending on
direction of approach in
See Section VII paragraph
setting up frequency with
2. Improper adjustment of course
the MEGACYCLES control
frequency oscillator coupler
Measure d-c voltage on
R-f output obtained only
1. Defective K-1501 relay
terminal 2 of coarse
on odd positions of
frequency oscillator.
MEGACYCLES control
2. Defective S-1503 switch
Should read 21V on even
mc steps. If not, check
switch S-1503
1. Normally closed contacts of
CARRIER meter red-lines
Check continuity with ohm-
but no 108 to 135.9 mc
meter and replace relay if
K-1401 failing to make contact
output at NAV comector
defective. Check continuity
2. Faulty r-f cables from attenuator
and connections of r-f
cables.
to K-1401 and/or from K-1401 to
NAV connector.
1. Normally open contacts of K-1401
CARRIER meter red-lines
Measure voltage across relay
failing to close when relay is
but no 329 to 335 mc output
terminals with NAV-GS switch
at GS connector
on GS. If 21V, check relay
energized.
for continuity. Replace if de-
2. Univerter circuits or r-f
fective. Check cables and
connecting cables bad.
make voltage and resistance
checks in univerter.
MICROVOLTS dial has
1. Improper alignment between
See Section VII paragraph
rough action.
attenuator shaft and front panel
control shaft.
2. Coupler sections fastened too
Loosen set screws in one or
closely together
both halves and re-set.
3. Need of lubrication on shaft
Apply lubrication, See Section IV
bearing points
R -F leakage
R-f covers not in place
Check for proper fit of cover
and missing screws
Attenuator tube set screws not
Tighten set screws (6) (7) and
tightened
(8), figure 7-6
Connectors improperly attached to
Check connectors.
coaxial cables at NAV -GS output
or at coaxial relay
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