Steps to pack a punch:
1.turn on power
2.shoot first bank door with ray gun(or any explosive) in the town to open it.
3.shoot second door behind that door with ray gun(or any explosive) as well.
4.use the turbine fan at the green lightning door in the power room.
5.a hatch will open in the bank vault where the other green lightning bolt was.
6.search for the stool, battery, and pack-a-punch shell in the new area.
7.build them on the workbench there.
NOTE! The turbine fan may die before you get back to the town, if it does you have to put another one there. Easiest way to do this: get a friend to place a turbine fan there while you are waiting at the vault in the bank
BTW the turbine FAN can also be used to buy perks when the power is out place it infront of the perk machine an buy away!!.
The turbine fan is the Doll/fan/battery/dont no wtf its called lol all can be found in the first room u spawn in in Transit.
You basically copy and pasted my thread word for word from Se7ensins, so if it's possible to update the OP and give me credit for the find that would be nice, thanks