TM  5-6115-332-14 TM  5-6115-332-14 P-8-614-14 P-8-614-14 TO  35C2-3-424-1 TO  35C2-3-424-1 CHAPTER 7 MAINTENANCE OF THE GENERATOR SET Section I. CONTROL BOX ASSEMBLY 7-1.  General This section covers direct support and general support maintenance of the control box and com- ponents. It includes the frequency converter, output  selector  switch,  relay  panel,  field  flash switch,  current  transformer  and  resistors,  voltage regulator  and  wiring.  All  components  are  accessible either by lowering the upper hinged panel or by removal of the lower access cover. Test  pro- cedures  are  included  when  applicable. CAUTION When plug P1 is connected, many of the meters are still active and need only a path to ground to complete circuit. 7-2.  Frequence  Converter a. General. The  frequency  converter  is  located near the center of the control box. It receives an ac signal of 120 volts from one of the generator coil groups and converts this signal voltage to a dc voltage  that  is  proportionate  to  the  frequency  of the generator output. The frequency meter is fed this.dc  voltage  and  the  meter  indicates  the  output frequency  in  Hertz. b.  Testing. Teat the frequency converter as follows: (1) Model MEP-071A. (a)   Apply   AC   input   of   120   volts,   60 hertz  current  across  terminals  marked “L”. (b) With panel  (M3)  connected  to  output side  meter  reading  should  indicate  60  hertz  + 0.5  hertz. (c)  For   teat   with   panel   meter   discon- nected, direct output current of the converter shall be 100 microamperes + 10 microamperes with  1100  ohm  load  across  positive  and  nega- tive  terminals. (2)  Model   MEP-022A. With generator set operating  at  3428  rpm,  remove  screw  in  the face of the frequency converter, and adjust the potentiometer  for  a  reading  of  400  HZ  on  the frequency meter. If   proper   reading   is   not obtained,  proceed  as  follows: (a) Disconnect the lead from the positive (+) and negative (-) terminals on the frequency meter. (b)  Attach   a   multimeter   with   the   scale set to read at least 200 microampere, to the + and  -  terminals  on  the  frequency  meter. (c)  Operate   generator   set   at   3428   rpm and turn adjusting screw to obtain a 100 micro- ampere on the multimeter scale. (d)  If   reading   is   accomplished,   the   fre- quency meter on the control panel is faulty and must  be  replaced. (e) If reading of 100 microampere cannot be obtained, disconnect the wire leads from the two  L  terminals  on  the  frequency  converter, Test  the  wire  leads.  If  no  defect  is  discovered, replace frequency converter and operate generator set. Turn  adjusting  screw  to  obtain  400  HZ reading. If frequency meter does not pass the above test, replace it. Refer to figure 5-1 and replace  the  meter  to  the  applicable  model  genera- tor set. c. Removal.  Refer to figure 7-1 and the follow- ing  instructions  to  remove  the  frequency  con- verter. Change 7 7-1