answer. In this way, the possible functional area of thefault is progressively narrowed. Tolerance values arepresented in those instances where a definitive yes or nois not obtained. This progression and elimination willallow you to isolate the functional area of the equipmentcontaining the fault. After lessening the possible causes,the diagram then refers you to the portion of the manualneeded to complete the fault isolation and repair. Eachdiagram includes, or makes reference to, theinformation necessary to establish the test or operatingconditions required for starting the fault isolationprocedure. The following three types of blocks are usedin fault logic diagrams.Shaded blocks (right and bottom border linesshaded) contain questions that may be answered fromobservation, without changing the test setup and withoutspecial equipmentSingle-line blocks contain questions requiringmeasurement by special setup of external test equipmentDouble-line blocks (conclusion blocks) list thefictional area within an equipment unit that is theprobable source of the malfunction and reference aprocedure or another diagram for further isolation orcorrection of a faultFunctional Dependency DiagramsThe FDDs are used to support troubleshooting ofthe gas turbine electronic power control system. AnFDD is a block diagram that illustrates the fictionaldependency of one test point (or circuit) upon another.Signal Flow DiagramThe signal flow diagram depicts the circuitry foreach of the main functions of the circuit that you aretroubleshooting. The notes preceding the signal flowdiagram contain instructions for establishing operatingconditions and connecting test equipment that isrequired for measuring the circuit parameters. For moreinformation on troubleshooting the LM2500, refer toPropulsion Gas Turbine Module LM2500, volume 2,part 1, NAVSEA S9234-AD-MMO-030/LM2500.ECSS TROUBLESHOOTINGPROCEDURESThis section will provide you with some simple, buthelpful, information when isolating a fault inengineering control and surveillance system (ECSS)equipment. Remember, many of the tips previouslymentioned are still applicable for electrical/electronicstroubleshooting. To successfully troubleshoot any pieceof ECSS equipment, you should keep the following fivesteps in mind:1.2.3.4.5.Energize the equipment to full operation usingthe appropriate EOP steps and equipmentlineups.Identify the faulting functional area.Locate the test and signal flow diagram relatingto the faulting component.Using the correct troubleshooting diagram,isolate the malfunction to the faultingreplaceable or adjustable subassembly.When a fault has been found to be in a specificr e p l a c e a b l e s u b a s s e m b l y , r e f e r t o t h eappropriate technical manual chapters forconnective maintenance instructions.When using the signal flow diagrams fortroubleshooting, you should begin at the malfunctioningcomponent and work back to the original signal source.By starting at the source of the problem, you should beable to identify and correct the problem in an efficientand timely manner.TROUBLESHOOTING DIAGRAMSThe types of troubleshooting diagramsused are theand chartssignal flow diagrams (description is given inprevious section),power distribution diagrams,logic flow charts,timing diagrams,interconnecting diagrams,troubleshooting functional dependencydiagrams, andthe circuit card locator and function informationplates.Power Distribution DiagramsPower distribution diagrams show the distributionof the primary ac power, secondary ac power, and thedc power from the input to the various components.2-27
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