04/07/21
Message Overview:
Message Description:
DBU is reporting a missing MDC bus input.
Possible Causes:
- Maintenance Diagnostic Computer (MDC) (A4-MDC)
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter: None
Quick Links:
| Component Location | AMM 45-45-00-992-801 |
| Operational Test of the Maintenance Diagnostic System | AMM 45-45-00-710-801 |
| Load the Maintenance Diagnostic Computer (MDC) Checklists | AMM 45-45-01-970-801 |
| Data Download from the Maintenance Diagnostic Computer (MDC) | AMM 45-45-01-970-802 |
| Load the Maintenance Diagnostic Tables (MDT) to the Maintenance Diagnostic Computer (MDC) | AMM 45-45-01-970-803 |
| Load the Test and Rigging Files to the Maintenance Diagnostic Computer (MDC) | AMM 45-45-01-970-804 |
| Removal of the Maintenance Diagnostic Computer (MDC) | AMM 45-45-01-000-801 |
| Installation of the Maintenance Diagnostic Computer (MDC) | AMM 45-45-01-400-801 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- Reset R IAPS Circuit Breaker CB2-B6 and DATA LOADER Circuit Breaker CB3-D1. Is the fault message still present?
- If NO, do close out.
- If YES, continue with next step.
- Do wiring check between IAPS Card Cage (A4) and DBU (A191) for the following wires:
From To Result Conn. A4P103 - 44 Conn. A191P1 - f Conn. A4P103 - 45 Conn. A191P1 - w - If check is satisfactory, continue with next step.
- If check is not satisfactory, repair defective wiring.
- Replace DBU (A191). Is the fault still present?
- If NO, do close out.
- If YES, continue with next step.
- Replace MDC. Is the fault message still present?
- If NO, do close out.
- If YES, continue with next step.
- Replace IAPS Card Cage (A4).
- Do close out.