400 Watt S51 High Pressure Sodium Quad Tap Ballast KitHPS Ballast Cross Reference: Advance Ballast 71A8473 001D Sylvania Ballast LU400 MULTI KIT Keystone HPS 400A Q HP Venture V90D1912K Sola E 871 W 411 Grainger 1A034 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