FREQUENCY  SENSING  CHECK  (HIGH  AND  LOW REF  DES Ra Rb,  RC M2., M3 Vl FREQUENCY) CONNECT  GOVERNOR  CONTROL  UNIT  TO TEST  EQUIPMENT  AS  SHOWN TURN  Ra  SO  THE  Resistance  BETWEEN P1-M  AND  Pl-T  IS  250  OHMS. REDUCE  THE  FREQUENCY  OF  THE  AP- PLIED 120 ± 2 VOLT SUPPLY UNTIL M2 AND  M3  BALANCE. THE  FREQUENCY  SHALL  BE  57-58  Hz. TURN Ra SO THE RESISTANCE BETWEEN P1-M AND P1-N IS 250 OHMS. INCREASE  THE  FREQUENCY  OF  THE  AP- PLIED 120 ± 2 VOLT SUPPLY UNTIL M2 AND  M3  BALANCE. THE  FREQUENCY  SHALL  BE  64-65  Hz. TEST  EQUIPMENT QUANTITY DESCRIPTION 1 POTENTIOMETER,  10  TURN,  500  OHM,  5  WATT 2 RESISTOR,  FIXED,  250  OHM,  5  WATT 2 MILLIAMMETER,  DC,  0-1000  MA DC POWER SOURCE AC POWER SOURCE ME  6115-545-34/7-4  C1 Figure   7-4.   Electric   Governor   Control   Unit,   Frequency   Sensing   Check   (High   and Low  Frequency)  (50/60  Hz) e.   Magnetic   Amplifier   Bias   Test   (50/60   Hz). Refer  to  figure  7-3  and  perform  the  magnetic  ampli- fier   bias   test. f.  Frequency  Sensing  Check,  High  and  Low Frquency  (50/60  Hz).  Refer  to  figure  7-4  and perform   the   frequency   sensing   check. g.   Rectifier   Bridge,   CR7   thru   CR30   and   Feed- back  Winding  Test  (50/60  Hz).  Refer  to  figure  7-5 and   perform   the   rectifier   bridge   and   feedback   winding test. h.   Parallel   Winding   Test   (50/60   Hz).   Refer   to figure   7-6   and   perform   the   parallel   winding   test. i.  Resistance  Test  (400  Hz).  Refer  to  Table  7-3 and   perform   resistance   test. j.  Magnetic  Amplifier  Bias  Test  (400  Hz).  Refer to   figure   7-7   and   perform   the   magnetic   amplifier   bias test. k.  Frequency  Sensing  Check,  High  and  Low Frequency  (400  Hz).  Refer  to  figure  7-8  and  per- form   the   frequency   sensing   check. L  Rectifier  Bridge,  CR7  thru  CRl0  and  Feed- back  Winding  Test  (400  Hz).  Refer  to  figure  7-9 7-6  Change  1 and   perform   the   rectifier   bridge   and   feedback winding   test. m.  Parallel  Winding  Test  (400  Hz).  Refer  to figure   7-10   and   perform   the   parallel   winding   test. n.  Replace  any  component  found  to  be  defective during   tests. o.   For   wiring   harness   repairs,   refer   to   Operator and   organizational   Maintenance   Manual. p.  If  wiring  harness  has  sustained  extensive damage,   refer   to   Chapter   5   for   wiring   harness rebuilding    procedures. 7-7.   Assembly. a.  See  figure  7-12  and  assemble  printed  circuit board.   If   any   connections   are   opened   or   bared   for test   purposes,   or   if   any   defective   components   are replaced,   the   effected   area   and   components   must   be coated   with   polyurethane   resin   to   prevent   oxidation or   other   corrosion   . The  coating  must  be  of  a  min- imum  thickness  of  0.007  inches  and  air  bubble  entry into  the  applied  polyurethane  must  be  controlled  so that  the  legibility  of  component  coding  and  identifi- cation  is  not  impaired.  The  polyurethane  resin  to be   utilized   will   correspond   to   MIL-I-46058,