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TM5-4120-376-14 b.   Brazing. (1)   Heat   evenly   to   recommended   temperature.    Keep   the   torch   moving   constantly   in   a “figure-eight’’   motion. (2)  Apply  silver  brazing  alloy  to  the  heated  parts. Do  not  heat  (melt)  the  silver  brazing alloy  with  the  torch. (3)   Cool   the   joint. (4)  Clean  the  joint,  using  warm  water  and  a  brush. (5)  Be  sure  all  flux  has  been  removed. 5-11.   LEAK   CHECKING. CAUTION Rapid   discharge   will   cause   oil   to   be   blown   out   of   the   compressor. NOTE The  electronic  leak  detector  is  sensitive  to  the  presence  of  refrigerant  gas (Table   D-1,   Item   11)   in   the   atmosphere.    When  refrigerant  gas  is  present  in  the atmosphere  of  the  work  area,  false  indications  can  result.  Use  in  a  well ventilated   but   draft-free   area. a.   Connect   a   manifold   gauge   to   the   suction   service   valve   on   the   unit   and   a   cylinder   of refrigerant  (Table  D-1,  Item  11).    Open  both  service  valves  and  the  cylinder  shutoff  valve.  Let refrigerant  flow  into  the  system  until  the  pressure  gauge  indicates  50  psig  (3.5  kg/cm2).   Close cylinder  shutoff  valve  and  suction  service  valve  and  disconnect  the  refrigerant  cylinder. b.  Connect  a  cylinder  of  dry  nitrogen  (Table  D-1,  Item  8)  to  the  suction  service  valve.  Open the   nitrogen   cylinder   shutoff   valve   and   the   suction   service   valve   and   pressurize   the   system   to 350  psig  (22  kg/cm2).  Close  both  valves  and  test  for  leaks  using  an  electronic  leak  detector  or the   soap   bubble   method   as   described   below: (1)  Electronic  Leak  Detector.  Turn  the  electronic  unit  on  and  slowly  pass  the  probe around   all   points   of   the   refrigeration   system   at   which   a   leak   could   exist.   Depending   upon   the type  of  detector  used,  leak  will  be  indicated  by  an  audible  signal,  a  light,  or  by  meter deflection. (2)   Soap   Solution.   Brush   soap   solution   on   all   possible   points   of   leakage   and   watch   for bubbles.  Follow  a  definite  sequence  to  avoid  missing  any  joints  that  should  be  tested.  Wipe  the solution  from  all  joints  and  mark  any  point  at  which  a  leak  is  found. (3)  Discharge  the  system  after  leak  checking  by  connecting  a  hose  to  the  suction  service valve  and  cracking  the  valve  open  slightly  to  slowly  discharge  the  gas.  If  leaks  were  detected, repair   them   and   retest   in   accordance   with   paragraph   5-11.   If   the   system   is   tight,   double evacuate   and   charge   the   system   in   accordance   with   paragraphs   5-12   and   5-13. 5-13

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