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 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. 2. 3. 4. 5. Energize   the   equipment   to   full   operation   using the   appropriate   EOP   steps   and   equipment lineups. Identify   the   faulting   functional   area. Locate  the  test  and  signal  flow  diagram  relating to   the   faulting   component. 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 r 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 e appropriate   technical   manual   chapters   for connective    maintenance    instructions. 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. 2-27