TM 55-4920-328-13 1.    Operator's    panel    assembly    3A1.        The operator's  panel  assembly  (1,  figure  1-24)  -is  installed  in the uppermost position of the sloping front section of the cabinet    assembly.        The    operator's    panel    assembly consists of a standard rackmounted chassis assembly 19 inches   wide,   4.34   inches   high   and   approximately   13 inches   deep,   excluding   the   length   of   the   slide   track assemblies.    The  chassis  assembly  is  provided  with  left and  right  handles  and  lock  release  pins  which  may  be disengaged   to   allow   the   chassis   assembly   to   be   tilted downward to upward to facilitate maintenance of the unit. The front panel is equipped with four openings.  The two left  cutouts  on  the  front  panel  are  used  for  mounting  a TORQUE   PRESSURE   indicator   M1   (2)   and   an   IGV ACTUATOR    ARM    indicator    M2    (3).        The    two    right openings  are  covered  with  sheet  metal  cover  plates  to exclude   foreign   matter   from   the   interior   of   the   unit. Terminal  boards  TB1,  TB2,  and  TB3  are  installed  in  the chassis   assembly   to   route   and   terminate   the   internal cabling   wire   runs.      Two   connectors,   J1   and   J2,   are installed   on   the   external   side   of   the   rear   panel   for interconnection  of  the  unit  with  other  components  of  the system.      The   two   blank   panels   are   removed,   when required,  for  installation  of  instrumentation  contained  in certain engine accessories.  A rectangular hole pattern is located  in  the  lower  left  portion  of  the  chassis  assembly for   mounting   an   inverter,   also   contained   in   an   engine accessories.  Refer to chapter 2 of this manual for further information on these components. a.    Torque   pressure   indicator   M1.      The   TORQUE PRESSURE  indicator  (2,  figure  1-24)  is  a  single-needle Autosyn     type     indicator     used     to     display     pressures transmitted  from  the  torque  system  through  a  pressure transmitter.  The indicator is graduated from 0 to 200 psig in    2-psi    increments.        Excitation    for    the    indicator    is provided by system 26v ac, 400 Hz power.  The indicator is supplied input signals from the pressure transmitter MT- 5.    The  two  instruments  comprise  a  functional  sub-loop. Movement   of   the   indicator   rotor   is   controlled   by   the strength of the magnetic field within the associated stator windings induced by input analog signals.  Rotation of the needle and rotor shaft is directly proportional to the input signal level supplied from the pressure transmitter. b.    IGV      Acutator   arm      indicator   M2.      The   IGV ACTUATOR     ARM     indicator     (3,     figure     124)     is     an instrument  that  provides  display  of  relative  positions  of the  engine  inlet  guide  vane  actuator  arm  during  a  test. 26v ac, 400 Hz excitation power is input to the instrument at connector pins A and B.  Analog signals from a remote IGV  actuator  arm  position  transmitter  connected  to  the data   acquisition   assembly   are   input   to   the   indicator. Needle  movement  to  display  inlet  guide  vane  actuator arm  position  is  provided  by  a  Magnesyn  type  assembly contained    in    the    indicator    case.        Movement    of    the indicator    rotor    is    influenced    by    the    strength    of    the magnetic    field    induced    within    the    associated    stator windings.    The  rotation  of  the  needle  and  rotor  shaft  is directly  proportional  to  the  input  signal  value  from  the transmitter. 2.    Operator's    panel    assembly    3A2.        The operator's panel assembly (7, figure 1-24) is located in the upper    portion    of    Unit    3    below    the    operator's    panel assembly 3A1.  This unit is similar to the panel assembly located immediately above.  The panel assembly consists of a rack-mounted chassis assembly 19 inches wide, 4.34 inches high, and 12.75 inches deep, excluding the length of the track slide assemblies.  Left and right handles and lock  release  pins  are  installed  on  the  front  panel  of  the chassis   assembly.      The   front   panel   also   mounts   an EXHAUST GAS TEMP meter M1 (38), a GAS PRODUCER  meter  M2  (4),  a  POWER  TURBINE  meter M3 (5), and an OIL TEMP meter M4 (6).  Terminal boards TB1 and TB2 are installed within the chassis assembly to route and terminate the internal cabling wire runs.  Three connectors  J1,  J2,  and  J3,  are  installed  on  the  external face  of  the  rear  panel  to  facilitate  interconnection  of  the operator's panel assembly with other units in the system. a.    Exhaust   gas   temp   meter   M1.      The   EXHAUST GAS   TEMP   meter   (38,   figure   1-24)   is   a   solid   state, combination pointer, indicating and digital counter type of instrument  used  to  display  exhaust  temperatures  of  an engine during a test.  The indicator senses an input signal from a chromel-alumel thermocouple junction.  The signal is   applied   to   a   cold   junction   compensation   unit   which compensates for ambient temperature changes within the instrument.  The compensator forms one leg of a bridge. Output  of  the  compensator  is  connected  through  a  filter, which  rejects  spurious  ac  line  frequencies,  to  a  chopper. The   other   leg   of   the   bridge   incorporates   a   slidewire potentiometer.        The    chopper    alternately    applies    the compensated   signal   and   the   potentiometer   signal   to   a servo  amplifier.    Unbalance  between  input  signals  to  the amplifier   results   in   a   generated   signal   which   drives   a servo mechanism.  The 1-43