Message Name:

AUDIO PANEL 1 MALFUNCTIONS

One or more Audio Panel functions do not operate correctly.

• Audio Panel Switch
• Audio Control Panel 1 (A8)
• Secondary Power Distribution Assembly (SPDA) 1 (A13)
• Secondary Power Distribution Assembly (SPDA) 4 (A16)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

1. Swap Audio Panel 1 with Audio Panel 2. Is the fault still present?

   1. If NO, go to step 12.
   2. If YES, continue with next step.

2. Disconnect Audio Panel 1 connector (A8P1) and perform a voltage check as follows:

   Audio Panel 1	Expected Result	Result
   A8P1-V	28 VDC
   A8P1-U	28 VDC
   A8P1-M	Ground

   1. If the power and/or ground value is not as specified above, investigate power sources (SPDA 1 or SPDA 4) or interface wiring and do close out.
   2. If the power and/or ground value is as specified above, continue with next step.

3. For Audio Bus, disconnect VHF COMM units 1 and 2 and VHF NAV units 1 and 2. Perform a continuity check as follows:

   From	To	Result
   A8P1-d	A1P1-56
   A8P1-p	A1P1-70
   A8P1-d	A3BP1-42
   A8P1-p	A3BP1-29
   A8P1-c	A2P1-56
   A8P1-n	A2P1-70
   A8P1-c	A4BP1-42
   A8P1-n	A4BP1-29

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

4. For Marker Sensitivity, disconnect Audio Panel 1 connector A8P2. Disconnect RMU 1 connector (A25P1) and RMU 2 connector (A26P1). Perform a continuity check as follows:

   From	To	Result
   A8P2-L	A25P1-h
   A8P2-L	A26P1-h

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

5. For IAC Aural Warnings, remove IAC 1 and IAC 2. Perform a continuity check as follows:

   From	To	Result
   A8P2-B	A11BP1-77
   A8P2-W	A11BP1-76
   A8P2-X	A10CP1-32
   A8P2-G	A10CP1-33

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

6. For Emergency Audio, remove VHF COMM unit 2. Perform a continuity check as follows:

   From	To	Result
   A8P1-G	A2P1-31
   A8P1-m	A2P1-29

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

7. For TCAS Voice, remove the TCAS unit. Perform a continuity check as follows:

   From	To	Result
   A8P2-t	A7EP1-3F
   A8P2-Z	A7EP1-3G

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

8. For GPWS Audio, remove the GPWS unit. Perform a continuity check as follows:

   From	To	Result
   A8P2-m	A64BP1-C13
   A8P2-J	A64BP1-D13

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

9. For CVR Interface, remove the CVR unit. Perform a continuity check as follows:

   From	To	Result
   A8P2-V	A51P1-43
   A8P2-r	A51P1-41

   1. If there is no continuity, repair defective wiring as required and do close out.
   2. If there is continuity, continue with next step.

10. For Cockpit Loudspeakers, refer 235OBS005.
11. Remove Audio panels 1, 2 and 3. Perform a resistance check of the Audio Bus Thermistors as follows:

    From	To	Expected result	Result
    A8P1-d	A8P1-p	R20 & R22=50 Ohms
    A8P1-c	A8P1-n	R21 & R23=50 Ohms

    1. If the resistance values are not as specified, repair defective wiring as required or replace the bus-termination resistors and do close out.
    2. If the resistance values are as specified, continue with next step.

12. Replace Audio Panel 1.
13. Do close out.