Telex Airman 8, Maintenance & Overhaul Manual

Page: 39 / 52

Airman 8 Maintenance 39
3.1.4 Microphone Troubleshooting and Workflow
3.1.4.1 Validate Continuity From Plug to PCBA
To validate continuity from the plug to the PCBA , do the following:
1. Using an Ohmmeter, place one probe on the ring terminal of the plug.
2. Place the other probe at J1 on the PCBA.
3. Record the measurement .
4. Using an Ohmmeter, place one probe on the sleeve terminal of the plug.
5. Place the other probe at J2 on the PCBA.
6. Record the measurement .
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If the reading is approximately 0, continuity is good.
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If any other reading is seen, the continuity is bad. Replace the cable.
3.1.4.2 Validate Mic PCBA
1. Construct a test circuit .
2. Connect the test circuit to the microphone plug of the headset.
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For more information, see “Connectors” on page 50.
3. Test for an audio signal .
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If audio signal is detected, the board the valid.
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If audio signal is not detected, the board should be replaced.
3.1.4.3 Microphone/Amplifier Sensitivity Check
IMPORTANT: The Airman 8 headset was designed, tested, and approved to FAA TSO C139a. The TSO
requires the headset meet the minimum performance specifications as defined in RTCA DO-
214a. This document and specifications listed here reference the test procedures and
equipment used as defined in these standards. Refer to the standard for details on how to
perform individual tests.
To test the sensitivity of the microphone , do the following:
1. Calibrate an artificial mouth .
2. Using the test circuit from the Mic validation and TSO procedures, measure the output
of the headset microphone with a digital volt meter .