150 Watt S55 High Pressure Sodium 120V Ballast KitHPS Ballast Cross Reference: Advance Ballast 71A8107 Sylvania Ballast LU150 120R Keystone HPS 150R 1 KIT MagneTek 1233 154U Venture V90B1422 High Intensity Discharge (HID) lamps require a ballast to apply starting voltage to the lamp and establish current flow an arc between the lamp electrodes. Without a ballast, the arc will extinguish or draw increasing current until some circuit element burns up. Ballasts provide system stability by limiting the