Message Name:

RMU DOES NOT FUNCTION PROPERLY

The Radio Management Unit (RMU) control functions do not operate correctly.

• Secondary Power Distribution Assembly (SPDA) 1 (A13)
• Secondary Power Distribution Assembly (SPDA) 4 (A16)
• Radio Management Unit (RMU) 1 (A25)
• Radio Management Unit (RMU) 2 (A26)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Are RMU 1 and 2 powered?

   1. If RMU 1 is not powered, troubleshoot power source from SPDA 1 and SPDA 4 and continue with next step.
   2. If RMU 2 is not powered, troubleshoot power source from SPDA 4 and continue with next step.
   3. If YES, continue with next step.

2. Check if the RMU display is magenta upon power up.

   1. If the RMU display is magenta upon power up, go to step 6.
   2. If the RMU display is not magenta upon power up, continue with next step.

3. During a cold start, the RMU performs a Power On Self Test (POST).

   1. If the test is satisfactory, the RMU displays the RADIO TUNING page.
   2. If the POST is not satisfactory, the RMU displays the SYSTEM TEST RESULTS or RADIO TEST RESULTS pages.

4. After the POST stops, does the RMU display the RADIO TUNING page?

   1. If YES, access the MAINTENANCE LOG page, record any fault codes displayed and go to step 7.
   2. If NO, continue with next step.

5. Check if the fault message RMU 1 (2) ERR and CHK RMU 1 (2) is displayed.

   1. If the fault message RMU 1 (2) ERR, go to step 8.
   2. If the fault message CHK RMU 1 (2), perform the RSB troubleshooting task and do close out.
   3. If both the fault messages are not displayed, access the MAINTENANCE LOG page, record any fault codes displayed and go to step 7.
      NOTE: An RMU shows the CHK RMU 1 (2) message if the opposite side RMU has an RSB fault or is not energized.

6. Remove the appropriate RMU and perform a continuity check on the following pins:

   RMU	Pin b	Pin c	Pin d
   RMU 1 (connector GM8)	Ground	Ground	Ground
   RMU 2 (connector GM9)	Open	Ground	Open

   1. If the strapping is not as shown in the table, repair defective wiring as required and do close out.
   2. If the strapping is good, go to step 8.

7. Check if any of the fault messages from the table below were recorded in step 4A or 5C:

   Fault Message	Fault Codes
   COMPUTER	06, 07, 09, 21, 23, 24, 26, 86, 87, 89, A0, A1, A3, A4, A5, A7, A9, 6E, EE
   A2D CONV	2B, AB
   LCD DIMM	62, AB
   LCD DRIV	63, 64, 66, 67, E3, E4, E6, E7
   PWR SPLY	69, E9, 6A, EA, 6B, EB

   1. If none of the fault message occur, do close out.
   2. If any of the fault message occur, continue with next step.

8. Replace defective RMU.
9. Do close out.