no question  those  are  graphtech  pickups.  first thing     loosen  the  screw  the  grounds  are   on  lift the   pcb and  make  sure  that  theres  some   electrical tape  or  something    that will insulate   the  back of the board   from the bridge  plate. if theres  nothing there  then  put  some  tape  on the  back of the pce.  those  wires  poke  through   the  back of thqat pcb and if they  touch the bridge  plate  they short out.  i just put my 300 in an epiphone  dot and   thats the first  thing i did  when installing  the   pickups.  insulate them  from  the bridge  plate.

  if that dont  do it  then check the  solder  oint  of the  bad  one. it  dont  look  that good  in the pic.  actually  none  of them do.

if thats not it then   strip the plastic  off the  crimped   grounds  and   add  solder to  those  clips      .. on both ends  to ake sure   there  are  no loose  grounds.   i just did  all that  on mine  and it  works  just fine  with the  graphtech  pickups. also dont go by that   generic  drawing  ast to being   a sign of  graphtech pickups.    its a cartoon   version  of something they should  have took a  photo for.

also     this person  did  do one thing  right,   they left  enough  wire  to redo the whole thing.

so  if you want to  just test the  pickup to see if its  good. unsolder  the  positive from the  pcb and put an ohm meter  on it  from positive to ground. that should tell you something.