Originally Posted by lighting123
1) what causes pulse start ballasts to fail (w/o the lamp)?
2) how long does the pulse start ballast take to wear out/fail?
1.) The ballast usually doesn't. The igniter. The igniter is only activated until the lamp is struck. But missing lamp will cause the igniter to continuously retry. The igniter can be made fail safe by including duration/attempts limit into each unit, but that would increase cost. The ballast doesn't need to be replaced if the external failed.
2.) That depends on operating temperature. Excess temperature will reduce life. This is not an easy question to answer. Core and coil ballasts aren't as likely to have sudden failure from surge and spikes like electronic ballasts.