TM 11-6625-928-35
CHAPTER 3
DIRECT AND GENERAL SUPPORT MAINTENANCE
Section I. GENERAL TROUBLESHOOTING INFORMATION
3-1. General Instructions
quired for testing the maintenance kit are listed in
The direct and general support maintenance pro-
cedures in this chapter includes troubleshooting,
Caution: Be careful when making test equip-
repair, and testing procedures for Test Facilities Kit
ment connections so that shorts will not be caused
MK-994/AR and MK-994A/AR. If Communication
by exposed test equipment connectors. Tape or
System Control C-6533/ARC, Heading-Radio Bearing
sleeve test prods or clips, as necessary, so as to
Indicator ID- 135 l/A, or Interconnecting Box J-
leave only as much bare metal exposed as needed
4247/AR does not work, replace the defective unit.
to make contact with the circuit under test.
For repair of the C-6533/ARC, refer to TM 11-5821-
262-35. For repair of the ID-1351/A, refer to TM 11-
3-4. Test Setup
5895-537-50.
3-2. Organization of Troubleshooting Procedures
Caution: To avoid transistor and integrated
circuit damage, make sure that all power switches
a. General. Perform troubleshooting by sectional-
are in the OFF position before changing cable
izing a fault to a major operating section and then
connections. Check the source voltage and polarity
localizing the fault to a defective assembly or
before making connections. Transistors and inte-
component.
grated circuits may be permanently damaged by
b. Sectionalization and Localization. Sectionalize
improper voltage or polarity. General support tests
faults by noting whether the fault occurred while
on the maintenance kit require connection to two
performing radio, communication system control, or
power sources (115 volts, 400 Hz, and 28 volts)
adf tests. Localize faults by referring to the trouble-
and to various test equipment. The 115-volt, 400-Hz
shooting chart for the section of the maintenance kit in
power source is only required when transformer T1
which the fault occurred (para 3-5).
is to be checked during adf test circuit tests (para
c. Visuald inspection. Visually inspect the mainte-
nance kit to see if faults can be sectionalized and
kit AC POWER connector J27 and the 115-volt,
localized without testing or measuring circuits.
400-Hz power source. Connect cable W22 between
Inspect for
Component
maintenance kit DC POWER connector J28 and
Circuit breakers---------- Secure mounting.
the 28-volt power source. Test equipment connec-
Selector switches--------- Secure mounting, ease of opera-
tions vary from test to test.
tion.
Cables (internal)--------- Proper connection.
3-5. Localizing Troubles
Test cables-------------- Broken connections or connec-
tors, shorted pins, or damaged
a. General. When a record has been made of the
pins.
conditions under Which the maintenance kit was
W i r i n g - - - - - - - - - - - - - - - - - - Broken connections, charred
found to be malfunctioning, consult the appropriate
insulation (evidence of over-
troubleshooting chart for information to localize
tions.
the trouble to a defective assembly or part. If a
F r o n t p a n e l - - - - - - - - - - - - - Evidence of physical damage or
malfunction occurred during the radio tests, refer
obliterated markings.
to the radio test circuit troubleshooting chart ( b
below); during the communication control tests,
d. Procedure. After the trouble has been localized,
refer to the communication system control test
replace the defective part or subassembly.
circuit troubleshooting chart (c below); during the
e. Intermittent troubles. Localize intermittent trou-
adf tests, refer to the adf test circuit troubleshooting
bles, if present, by tapping or jarring the mainte-
chart (d below).
nance kit.
Note. The information presented in the following charts
3-3. Test Equipment Required
is applicable when the COMM CONT NO. 1 VOL control
Test equipment, tools, materials, and facilities re-
is adjusted for maximum audio gain.
3-1
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