TM 55-4920-328-13 1. Services    panel    assembly    4A12.        The services panel assembly (1, figure 1-25) is located at the uppermost  position  in  the  cabinet  assembly.    The  unit consists    of    a    standard    width,    rackmounted    chassis assembly which mounts seven water brake performance      analyzer   meters      M1   through   M7   (2 through  8).    The  chassis  assembly  is  provided  with  a pair  of  front-mounted  handles  and  left  and  right  track slide  assemblies.    Locking  notches  in  the  track  slide assemblies are engaged by left and right lockpins.  The lockpins  may  be  disengaged  from  the  notches  to  allow the  chassis  assembly  to  be  rotated,  once  the  chassis assembly   is   pulled   away   from   the   cabinet   assembly. This action will provide convenient access to components  during  maintenance;  the  chassis  may  be rotated to any of three positions.  Six bracket mounted, modular    28v    dc    precision    power    supply    units    are contained   in   the   services   panel   assembly   to   provide [signal    transmission    power    for    the    system.        Three terminal  board  assemblies  route  the  internal  wiring  of the unit.  Connection of the services panel assembly is made through three connectors J1, J2, and J3, mounted on the rear panel. a. Water brake performance analyzer.  meters M1 through    M7.        The    services    sub-module    assembly contains seven dc-operated meters (2 through 8, figure 1-25) which display temperature and pressure (indications  monitored  on  a  water  brake  dynamometer used  as  a  power  absorption  device  during  an  engine test).          Five     of     the     meters     display     temperature indications;  the  other  two  provide  pressure  indications. The five temperature meters M1, M2, M3, M4, and M7 are  identical  in  design,  function,  and  scale  markings; only one will be described.  The temperature meter is a vertical   scale,   bottom   zero,   dc-operated,   D'Arsonval movement  enclosed  in  a  rectangular  housing.    A  zero adjustment  is  located  on  the  center  of  the  rear  face  of the  meter  housing.    The  meter  operates  over  an  input current  range  of  0  to  18  madc.    Input  signals  to  the meter   are   provided   by   Type   Y(BS)   iron-constantan thermocouple  networks.    Refer  to  table  1-1  for  other leading  particulars  of  the  temperature  meter.    The  two pressure meters M5 and M6 are identical and only one need be described.  The internal movement and housing are    similar    to    the    temperature    meter.        The    scale markings  of  the  pressure  meter  range  from  -30  inches hg  to  250  psig.    The  meter  operates  on  input  voltages ranging  from  0  to  5v  dc.    Additional  leading      TM  55- 4920-328-13      particulars   of   the   pressure   meter   are contained in table 1-1. b. Power supply unit.  The system incorporates six modular 28v dc precision power supply units (56, figure 7-18)   installed   in   the   services   panel   assembly   4A12. One  of  the  six  power  supply  units  provides  excitation power  for  the  water  brake  water  pressure  in  and  out circuits.    Indications  of  pressure  are  displayed  on  the WATER  PRESSURE  IN  meter  (4,  figure  1-25)  and  the WATER  PRESSURE  OUT  meter  (5).    The  other  five power supply units individually provide excitation power for   the   other   five   meters   on   the   WATER   BRAKE PERFORMANCE ANALYZER panel.  The power supply units are identical; therefore, only one will be described. Each power supply unit consists of a transformer, power transistors,    diodes,    capacitors,    resistors,    and    other electrical    components    mounted    on    a    plate.        The secondary  of  the  transformer  is  coupled  to  a  full  wave bridge  rectifier  and  to  the  solid  state  components  on  a circuit board assembly.  The power supply is energized from the system 117v ac, 60 Hz power provided by the diesel engine generator set.  Output of the power supply is adjustable between 0 to 30v dc.  Refer to table 1-1 for other  leading  particulars  of  the  28v  dc  precision  power supply. 2.    Services    panel    assembly    4A1.    The services   panel   assembly   (9,   figure   1-25)   is   located immediately  below  the  services  panel  assembly  4A12 (1).      This   panel   assembly   consists   essentially   of   a chassis  assembly  which  mounts  a  digital  elapsed  time indicator,  an  alarm  display  indicator  assembly,  and  a series   of   switchlight   units   at   the   bottom   of   the   front panel.      The   chassis   assembly   is   a   standard   rack- mounted   unit   19   inches   wide,   8.72   inches   high,   and approximately  13  inches  deep.    The  chassis  assembly also mounts two identical relay box assembles installed -on  the  inside  face  of  the  rear  panel  to  accommodate relays  K1  and  K2.    Two  terminal  boards  TB1  and  TB2 are   installed   in   the   chassis   assembly   to   route   and terminate   the   internal   wiring   of   the   services   panel assembly.    The  chassis  assembly  is  also  provided  with frontmounted  left  and  right  handles,  two  lock  release pins, and a pair of track slide assemblies.  The locking feature   of   the   lock   release   pins   is   identical   to   the services   panel   assembly   4A12,   located   immediately above.  The front panel of the chassis assembly mounts the   following   annunciator-type   indicators   depicted   in figure 1-25: 1-49