When looking out of the barrack's window, Hogan points out the radio detector truck in the compound to the others. Shortly after, when LeBeau, Carter and Newkirk cut off Kinchloe's radio transmission, Newkirk says the detector truck is outside the compound.
Hogan's birthday cake has 4 "candles" on it that the gang intends to use to fire at the radio truck. In the next closeup scene of the truck, 3 shooting candles make a direct hit into the open door. In the following wide shot, the cake only has two lit candles while two candles are still unlit.
Update: Only one 'candle' is ever lighted. The one candle shoots three times, but only one of the shots goes in the door of the truck. After the three shots go off, the next time the cake is shown is when Schultz goes over to the cake before going to the radio detector truck. When the cake is shown in that shot, the cake is at the extreme left side of the view, and the one burned 'candle' is barely visible at the extreme edge of the view.
Update: Only one 'candle' is ever lighted. The one candle shoots three times, but only one of the shots goes in the door of the truck. After the three shots go off, the next time the cake is shown is when Schultz goes over to the cake before going to the radio detector truck. When the cake is shown in that shot, the cake is at the extreme left side of the view, and the one burned 'candle' is barely visible at the extreme edge of the view.
Kinch's orange noisemaker disappears off the table after he puts it down.
After the 'candle' is done shooting, Klink tells Schultz to go check on the radio detector truck. Before doing so, he goes over to Hogan and asks Hogan to save him a piece of cake. The candle that was lighted and shot the smokers into the truck is barely visible at the left side of the view, and is black at the top end, but is NOT burning. Schultz runs out of frame to the right, and then there is a cut to a wide shot with the cake in the center. The candle that shot the smokers is now burning.
Sgt. Schultz suggest baking a German chocolate cake for Col. Hogan's birthday. German chocolate cake was really invented in the United States and wasn't well-known even there until after World War Two.