TM 1-1520-238-T-6 9–235 9–57. LT NAV CIRCUIT BREAKER (CB73) – DOES NOT STAY CLOSED 9–57 Tools: Nomenclature Part Number Tool Kit, Electrical SC518099CLA06 Repairer’s Multimeter, Digital AN/PSM-45 Personnel Required: 68X Armament/Electrical Systems Repairer References: TM 1-1520-238-23 WARNING Turn off power before detaching or attaching wires and connectors. High current 28 VDC or 115 VAC is present. Failure to do so could result in death or serious injury. 1. On pilot center circuit breaker panel, open NAV LT circuit breaker (CB73). Check for short between P1-25 and ground. Does short exist? YES Go to paragraph 9–220 to troubleshoot circuit protection system (dc essential bus 2 – pilot station). NO Go to step 2. 2. Detach P1. Check for short between P100-B20 and ground. Does short exist? YES Repair shorted wire between: P100-B20 and P457-A1, (A402)J1-25 and (A402)J22-A15. Go to paragraph 9–55. NO Go to step 3. 3. Remove left navigation light (TM 1-1520-238-23). Check for short between P100-A20 and ground. Does short exist? YES Repair shorted wire between: P100-A20 and J115-7, P115-7 and XDS5-1. Go to paragraph 9–55. NO Go to step 4. 4. Remove right navigation light (TM 55-1520-238-23). Check for short between P100-B14 and ground. Does short exist? YES Repair shorted wire between: P100-B14 and J448-B10, P448-B10 and J116-7, P116-7 and XDS6-1. Go to paragraph 9–55. NO Go to step 5. 5. Remove tail navigation light (TM 55-1520-238-23). Check for short between P100-B15 and ground. Does short exist? YES Repair shorted wire between: P100-B15 and P457-A6, P431-A1 and J410-A13, P410-A13 and J124-17, P124-17 and J1012-3, P1012-3 and XDS7-1, (A402)J22-A6 and (A402)TB3-16-D, (A402)TB3-16-E and (A402)J27-A1. Go to paragraph 9–55. NO Replace pilot EXT LT/INTR LT panel (TM 1-1520-238-23). END OF TASK