12-23. OPERATIONAL CHECK.
Before beginning the operational check, install a new holding battery to replace the holding battery removed for
The operational check provides a step-by-step procedure for evaluating an RCU. If the operational check is
passed, the RCU can be returned to service. If it is not, the bad module or the troubleshooting chart to be used
will be identified. The troubleshooting flowcharts are in paragraph 12-24.
The operational check is divided into numbered steps. Each step verifies a particular function. Read through
each Action and Response before performing the Action. Follow the instruction in the Action column of
each lettered substep. Check the response. If the response is correct, proceed with the next lettered substep.
When a numbered step has been completed, proceed with the next step. A No response in the a Response
column means that any response is not of interest.
The switch settings for the test equipment are given in the Set: section at the start of each numbered step.
Set the test equipment switches to the indicated presets and then verify the settings. If a test response is
incorrect, check the equipment settings and the test adapter cabling before going to a troubleshooting chart or
replacing a bad module.
Connect the test setups only when directed, and with the power supply set to OFF. The large
current capacity of the test power supply can cause personal injury. Verify the test setup before
turning the power supply on.
Whenever either cover is removed, take all proper electrostatic discharge (ESD) precautions.
Static electricity can damage the RCU modules.
Step 1. SAFE TO TURN ON CHECK.
a. Connect and set equipment as shown in
b. Connect DMM (+) to TP9 and DMM (-) to
TP12. Set DMM to 200 k ohms scale.
c. Set RCU: SPKR:
a. No response.
b. DMM reading is greater than 18 k ohms.
If not, go to chart 1.
c. DMM reading is greater than 2 k ohms.
If not, go to chart 2.