For these codes to work you need to load/reset the game and then execute the BASIC commands before running or restarting the game. The Unlimited Weapons cheat is two lines, one after the other.

Code - Effect

POKE 9825,173 - Unlimited Energy
POKE 12303,173 - Unlimited Lives
POKE 5847,173 - Unlimited Missiles
POKE 10641,173 - Unlimited Time
POKE 5014,173 - Unlimited Weapons (part one)
POKE 6424,189 - Unlimited Weapons (part two)