Preheat the oven to 350 degrees F (175 degrees C). Bring a saucepan of lightly salted water to a boil. Add pasta, and cook for 8 to 10 minutes or until al dente; drain.
Cook ground beef in a skillet over medium heat, stirring until evenly browned; drain. Stir in cooked macaroni, condensed soup, milk, and ketchup until well blended. Mix in the Cheddar cheese, green pepper, and minced onion. Season with salt, and pour into a 2 quart baking dish.
Cover, and bake for 40 minutes in the preheated oven. Uncover, sprinkle the top with potato chips, and bake for another 5 to 10 minutes, until chips are toasted.