A loco that had been using the NCE ATL-S4 decoder was retrofitted with the sound decoder. as shown here. This install is putting 5-1/2 pounds of stuff in a 5 pound bag - not for the feint of heart.
Sunny white LEDs were mounted to the shell with their resistors wired in series. These days, I’d use the 3 mm 12 volt warm white LEDs - no resistor needed. Opaque (metal foil) tape was used inside the nose of the loco to prevent light leakage.
The speaker was mounted in the cab with the cone facing toward the truck and adjusted as far down as it could be without interference with the truck throughout its entire range of motion. The speaker and LED wires were brought out and black styrene used to enclose the speaker rear area.
Initially (when this photo was taken) the Tsunami was mounted to a piece of black styrene. In operation, after about an hour, the loco would start to show signs of thermal shutdown. The fix was to build a shelf with brass that was raised up on pieces of brass over the front truck - an upside down U assembly was built to clear the drive line. This brass assembly was held to the frame with silver epoxy to maximize heat transfer. The Micro Tsunami was held down to the brass sheet with bathtub caulk. After this modification, the loco was operated 8 - 10 hours a day for two weeks without any indication of overheating. The nose of the shell was warm to the touch.