The B9503 is the EcTronic control board used across the Berson InLine and ProffLine ranges. It carries the lamp supervision, wiper drive and alarm logic that the plant runs on, so a failed board takes the whole reactor out of service even when lamps and sleeves are sound. Original Berson number 6.40.005*1. The fitment list below is long because one board covers most of the range — check the number printed on the board itself before ordering, as later systems moved to the EcTronic+ and Omega boards, which are not interchangeable with this one.