Section  II.  BATTERY  CHARGING  ALTERNATOR 14-8.   General. a.   The   28   volt,   35   ampere   battery   charging   alter- nator   system   is   specifically   designed   for   applications which   require   enclosed   brush   and   slip   ring   construc- tion.   All   of   the   aluminum   casting   and   exposed   parts are   coated   or   plated   to   prevent   corrosion.   Both   front and   rear   bearings   are   sealed   and   lubricated   for   life. b.  The  brush  assembly,  enclosed  by  the  rear housing   cover,   positions   the   brushes   and   provides the   necessary   pressure   for   good   electrical   contact with   the   slip   rings.   The   voltage   adjusting   rheostat   is a   screwdriver   adjustment   accessible   through   a   hole in  the  rear  cover  of  the  alternator.  Remove  battery charging   alternator   in   accordance   with   Operator   and Organizational    Maintenance    Manual. 14-9.  On  Equipment  Test. a.   Rear   Cover   Removal. With  the  engine  gener- ator  get  stopped  remove  the  3  self  tapping  screws securing   the   rear   cover   of   the   battery   charging alternator   to   the   alternator   housing.   Remove   the rear  cover  plate  and  leave  it  suspended  by  the  at- tached   wiring.   Remove   the   40   ampere   fuse   from its   receptacle. CAUTION Insulate   all   wiring   to   the   rear   cover   plate by   inserting   insulating   material   between the  alternator  housing  and  wiring  to  the rear   cover   plate. b.   Voltage   Regulator   Test   Connections.   Connect the  test  equipment  to  the  alternator  as  shown  in figure   14-1. c.   Voltage   Regulator   Test   and   Adjustment. — (1)  Start  the  engine,  allow  a  few  minutes  for warm   up.   Assure   that   the   alternator   drive   sped   is between   2000   to   3000   rpm.   Indicated   frequencies for  50,  60  or  400  Hz  will  provide  the  required  battery charging  alternator  drive  speeds  for  the  respective engine-generator     sets. (2)   Observe   the   test   ammeter.   A   test   ammeter reading  in  excess   of  10  amperes  is  indicative  of  low batteries.   If   the   test   ammeter   reading   exceeds   10 amperes,   remove   the   jumper   from   the   1/4   ohm   50 watt  resistor  thereby  reducing  alternator  output  cur- rent,   by   its   insertion   in   the   circuit. (3)   Observe   the   test   voltmeter.   The   test voltmeter  should  indicate  28.0  Vdc  ±  .3  V  at  75 degrees   F. (4)  If  the  test  voltmeter  does  not  indicate  the required   voltage,   use   a   small   screw   driver   to   adjust the   rheostat   on   the   voltage   regulator   to   raise   or lower   the   charging   voltage. 14-2 (5)  Shut  down  the  engine-generator  set  and  dis- connect   the   test   equipment. d.  Alternator  Output  Test  Connections.  Connect the  test  equipment  to  the  alternator   as   shown   in   figure 14-1. (1)   This   test   will   determine   if   the   alternator   is capable   of   producing   its   minimum   rated   output.   This is  an  evaluation  of  the  rotor,  stator  and  all  diodes  and their   ability   to   produce   current.   While   maximum   at- put   depends   on   alternator   temperature,   the   minimum acceptable  output  is  used  for  reference.  The  charging system   is   also   tested   under   partial   load   to   determine if   excessive   voltage   loss   exists   between   the   alternator and   the   battery   through   the   circuit   conductors. (2)   Start   the   engine-generator   set,   run   the   en- gine   at   approximately   750   RPM.   If   the   test   ammeter indicates   less   than   10   amperes   charge,   slowly   apply the   load   across   the   battery   until   the   ammeter   indi- cates  10  amperes. Let  the  engine  run  in  this  man- ner   for   5   minutes   to   stabilize   component   tempera- tures   within   the   alternator   and   its   integral   solid state  regulator. (3)  Note  voltage  loss  incurred  by  moving  the positive   voltmeter   lead   from   the   positive   output   term- inal   to   the   battery   positive   post,   with   the   alternator producing   10   amperes. If   the   loss   exceeds   0.2   volts, check   for   poor   connections   or   undersized   conductors, repair   as   necessary. (4)   Increase   set   speed   to   rated   speed   (50,   60 or   400   Hz).   Increase   load   on   the   battery   causing the  alternator  to  deliver  its  maximum  current  capa- city  of  35  amperes  indicated  on  the  test  ammeter. (5)  Shut  down  the  engine-generator  set  and  dis- connect   the   test   equipment. e.  Voltage  Protector  Test  Connections. — (1)   The   voltage   protector   test   configuration   is that  which  occurs  when  the  rear  cover  of  the  battery charging  alternator  is  removed  from  the  alternator housing,  with  the  additional  connection  of  the  test  volt- meter   according   to   polarity,   to   the   positive   and   neg- ative  output  terminals. (2)  Start  the  engine-generator  set,  adjust  the throttle  to  obtain  rated  speed,  run  a  few  minutes  to normalize   temperature   of   the   charging   system,   note the   charging   voltage. (3)  Remove  one  cable  from,  one  battery  post, and  note  the  charging  voltage. (4)  If  the  charging  voltage  without  the  battery  in the   circuit   exceeds   31.0   volts,   the   voltage   protector   is defective   and   must   be   replaced. (5)   Shut   down   the   engine-generator   set.   Dis-