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TM 11-5821-333-12
Section IV. TROUBLESHOOTING RADIOS
Subject
Para
Page
Explanation of Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-14
6-10
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-12
6-4
How to Use Flowcharts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-15
6-10
Operational Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-13
6-4
Troubleshooting Flowcharts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16
6-11
6-12. GENERAL.
This section has an operational check and troubleshooting flowcharts. They are used to find the bad unit in a
radio set, When a failure is reported, do the following:
a. Inspect radio set components for damage. Repair any damage before proceeding.
b. Do the operational check.
c. Do any troubleshooting called for by the operational check.
d. Replace the defective unit.
e. Verify the repair by doing all the operational check.
6-13. OPERATIONAL CHECK.
NOTE
These tests are for RT-1476, RT-1476A, RT-1477, and RT-1477A radios.
For RT-1478 and RT-1478A radios, see aircraft system technical manual.
The operational check is a series of steps used to evaluate equipment operation. These steps should be done
with the equipment installed in the aircraft. Bench tests alone do not ensure that the radio set will function
correctly. These steps are also used for PMCS and to verify equipment is good after repair.
a. Test Description. Each step checks the response of the radio to an operator action. The steps are
numbered so they can be used for reference on maintenance worksheets. Each step is titled according to the
function being checked. This is for use by the experienced workman. The details are provided for novices.
b. How to Proceed. If normal results are found, proceed to the next step. If abnormal results are found,
replace the indicated unit or go the the indicated troubleshooting flowchart.
ACTION
RESPONSE
Step 1. DRA SELF-TEST.
a. If KY-58/TSEC is present, set its MODE to P.
a. No response.
b. If DRA not present, go to step 2.
b. No response.
c. Set RT/RCU FCTN switch to OFF.
c. No response.
d. Listen to headset. Switch circuit breaker for
d. Short two-tone beep. If not, go to chart 1
DRA to OFF then back to ON.
(page 6-11). If continuous 1200-Hz tone is
heard, replace DRA.
6-4
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