TM 55-4920-328-13 5-12.  Checkout of Position Transmitters. The IGV and throttle position transmitters provided in the  engine  accessories  may  not  be  electrically  isolated from   the   system   and   individually   checked.      These components are synchronous instrumentation and must be   checked   while   installed   in   a   system   or   functional loop.      (See   figure   FO-22   located   in   the   back   of   the manual.)  Refer  to  paragraph  5-38  for  troubleshooting information on the IGV and throttle position transmitters. 5-13.  Checkout of Thermocouples. Thermocouple  checkout  consists  only  of  a  continuity check; however, if a thermocouple is suspected of being defective the unit may be removed from the system and a  like  part  number  thermocouple  may  be  connected. The jet-cal analyzer may be used on EGT thermocouples for some engines. 5-14.  Checkout of Vibration Pickups. The   vibration   pickup   may   be   lightly   tapped,   when electrically   connected,   to   provide   a   response   on   the vibration meter in the control cab.  The pickups provided in   the   engine   accessories   may   be   interchanged   by substitution  for  fault  isolation  during  daily  checkout,  if the same part number is substituted. 5-15.  Pressure Gage Switch Checkout. Pressure gage switches (170, 181, 184C, figure 7-24) may  be  functionally  checked  without  removal  from  the data acquisition assembly.  Check the actuation of each pressure   gage   switch   on   increasing   and   decreasing pressures in accordance with the following: a.        Connect    a    pressure    hose    with    appropriate connectors to the test trailer suspect pressure switch on the data acquisition box, Unit 11. b.  Turn the SERVICES AIR switch to ON, and slowly adjust    the    Pressure    Regulator    while    watching    the pressure   gage,   (all   on   panel   9A2).      Verify   that   the indicator    light    associated    with    the    pressure    switch activates on or off as the case may be, at the specified pressures. c.   Substitute cabling by switching connections at the back of the switches, to verify lead defects, and applying pressure as above. d.  Pressure switches S1, S2, and S3 shall actuate as follows. S1, Low  Fuel  Pressure,  indicator  light  (Panel  4A1) extinguishes at pressure above 8.0 PSI. S2, Engine  Low  Oil  Pressure,  indicator  light  (Panel 4A1) extinguishes at pressure above 30 PSI. S3, Hot  Air  Pressure,  activates  the  DE-ICE  VALVE OPEN,  and  DE-ICE  VALVE  CLOSED  lights  on operators panel 3A3.  The CLOSED light should be ON for all engines except the T-73.  With a pressure of approximately 4.5 PSI the CLOSED light  should  extinguish  and  the  OPEN  light  will come ON. e.    If  any  pressure  gage  switch  does  not  actuate  on both   increasing   and   decreasing   pressures   within   the specified   limits   for   each   unit,   depressurize   the   test setup,  remove  the  defective  switch,  then  install  a  new unit.    Check  the  actuation  of  the  replacement  unit  on both increasing and decreasing pressures as outlined in the foregoing instructions. f.        After    functional    check    of    the    pressure    gage switches,   depressurize   and   dismantle   and   test   setup. Reconnect    the    electrical    system    connectors    to    the respective    pressure    gage    switches    and    install    the removed dust caps on the quick-disconnect couplers. 5-16.  Warning Circuit Checkout Procedures. This  paragraph  contains  the  procedures  required  to check  the  METS  warning  circuits  on  a  periodic  basis. Proceed as follows: a.      With   the   electrical   system   energized   and   the specified  warmup  accomplished,  depress  and  hold  the TEST    switchlight    unit    (26,    figure    1-25)    located    on services   panel   4A1.      Verify   that   the   entire   ALARM DISPLAY   intermittently   flashes   on   and   off   and   the audible alarm sounds continuously. b.  With the TEST switchlight unit depressed, depress and release the ACK switchlight unit (25).  Verify that all ALARM  DISPLAY  indicators  come  on  and  stay  on  and that  the  audible  alarm  ceases  to  sound.    If  any  of  the alarm  lights  fail  to  come  on,  the  problem  will  be  in  the alarm card in the Alarm Monitor unit 4A2.  Refer to the troubleshooting,   table   5-4,   or   the   alarm   verification tables for alarm card identification.  Each card contains two   separate   channels,   and   each   channel   functions independently.    Four  spare  cards  are  available  within the alarm monitor unit 4A2 for substitution. 5-7