TROUBLESHOOTING As a GS supervisor, you will find that successful troubleshooting is a rewarding experience. Proper use of the manufacturer's technical manual will enhance your professional abilities and result in getting the job done right the first time. This section discusses the use of the troubleshooting sections of the LM2500 GTE technical manual.

TROUBLESHOOTING TECHNIQUES Troubleshooting is a systematic analysis of symptoms that indicate an equipment malfunction. These symptoms usually appear as deviations from the normal parameters. You must be able to recognize normal operating conditions to recognize abnormal operation. If you have a thorough knowledge of equipment systems and use logical reasoning, you will be able to solve most troubleshooting problems with little difficulty. The basic methods used during mechanical and electrical/ electronic troubleshooting are as follows:

Be sure you know the normal operating conditions (be able to recognize a problem).

Find out everything about the nature of the malfunction. Write down all the symptoms and see if they follow an identifiable pattern.

Check the obvious: -Blown fuses -Tripped circuit breakers -Faulty alarms

-Loose connectors and cannon plugs -Switches in the wrong position -Burned-out lamps

-Physical damages -Last PMS or maintenance procedure performed -System alignment

LM2500 TROUBLE ISOLATION The trouble isolation section (volume 2) of the LM2500 technical manual contains three chapters with troubleshooting information that will aid you in isolating faults and malfunctions in the LM2500 GTE and its ancillary equipment. The manual presents troubleshooting procedures in fault logic diagrams, fictional dependency diagrams (FDDs), and signal flow diagrams.

Fault Logic Diagrams These diagrams are based on a fault indication observed during troubleshooting. The diagrams comprise a branching series of questions pertaining to fault isolation. Each question pertains to further observation or measurement, and results in a yes or no answer. In this way, the possible functional area of the fault is progressively narrowed. Tolerance values are presented in those instances where a definitive yes or no is not obtained. This progression and elimination will allow you to isolate the functional area of the equipment containing the fault. After lessening the possible causes, the diagram then refers you to the portion of the manual needed to complete the fault isolation and repair. Each diagram includes, or makes reference to, the information necessary to establish the test or operating conditions required for starting the fault isolation procedure. The following three types of blocks are used in fault logic diagrams.

* Shaded blocks (right and bottom border lines shaded) contain questions that may be answered from observation, without changing the test setup and without special equipment

l Single-line blocks contain questions requiring measurement by special setup of external test equipment

. Double-line blocks (conclusion blocks) list the fictional area within an equipment unit that is the probable source of the malfunction and reference a procedure or another diagram for further isolation or correction of a fault

Functional Dependency Diagrams The FDDs are used to support troubleshooting of the gas turbine electronic power control system. An FDD is a block diagram that illustrates the fictional dependency of one test point (or circuit) upon another.

Signal Flow Diagram The signal flow diagram depicts the circuitry for each of the main functions of the circuit that you are troubleshooting. The notes preceding the signal flow diagram contain instructions for establishing operating conditions and connecting test equipment that is required for measuring the circuit parameters. For more information on troubleshooting the LM2500, refer to Propulsion Gas Turbine Module LM2500, volume 2, part 1, NAVSEA S9234-AD-MMO-030/ LM2500.

ECSS TROUBLESHOOTING PROCEDURES

This section will provide you with some simple, but helpful, information when isolating a fault in engineering control and surveillance system (ECSS) equipment. Remember, many of the tips previously mentioned are still applicable for electrical/ electronics troubleshooting. To successfully troubleshoot any piece of ECSS equipment, you should keep the following five steps in mind:

1. Energize the equipment to full operation using the appropriate EOP steps and equipment lineups.

2. Identify the faulting functional area.

3. Locate the test and signal flow diagram relating to the faulting component.

4. Using the correct troubleshooting diagram, isolate the malfunction to the faulting replaceable or adjustable subassembly. When a fault has been found to be in a specific replaceable subassembly ,refer to the appropriate technical manual chapters for connective maintenance instructions.

5. When using the signal flow diagrams for troubleshooting, you should begin at the malfunctioning component and work back to the original signal source. By starting at the source of the problem, you should be able to identify and correct the problem in an efficient and timely manner.

TROUBLESHOOTING DIAGRAMS The types of troubleshooting diagrams used are the and charts signal flow diagrams (description is given in previous section), power distribution diagrams, logic flow charts, timing diagrams, interconnecting diagrams, troubleshooting functional dependency diagrams, and the circuit card locator and function information plates.

Power Distribution Diagrams Power distribution diagrams show the distribution of the primary ac power, secondary ac power, and the dc power from the input to the various components.

Logic Flow Charts Logic flow charts have the event sequences as determined by the logic circuits. The charts are, in effect, pictures of the logic equations. They maybe used along with the logic equations found in chapter 3 of the S9234-series technical manuals.

Timing Diagrams Timing diagrams are for all significant timing relationships. The diagrams show the exact timing relationships and the origin of all significant timing signals.

Interconnecting Diagrams Interconnecting diagrams show the internal cabling between the consoles and the electronic enclosures. These diagrams identify the cabling and components by reference designations.

Troubleshooting Functional Dependency Diagrams Troubleshooting fictional dependency diagrams (TFDDs) show the fictional dependency of one circuit upon another. The TFDDs are setup in pyramid fashion. The vertical chains of boxes show contributing branches of the signal development. They also show the fictional dependency through successive levels. The box at the top represents the function output of the equipment and reflects the results of all of the boxes below it.

Circuit Card Locator and Function Information Plates Circuit card locator and function information plates (troubleshooting matrices) present the maintenance information you need to isolate a specific circuit card location. The matrix for troubleshooting is on the inside of the door of each electronic cabinet assembly (ECA).

The matrix relates the ship functions to the supporting circuit card within the ECA. The ship function column lists the ship function controlled or monitored. The qualifier column identifies the specific function listed in the function column. The type column identifies the function as a control, status, or alarm function. The card location column contains the card locations within the ECA. An X in the card location column indicates that the circuit card is in that location in the ECA card rack. The listings in the ship function column relate to the identities of the discrete panel readouts rather than the fictional groupings. The troubleshooting matrix can be used in conjunction with the demand display directories.