Power booster for slide projectors

The lamp in slide projectors is normally controlled with the aid of a triac in series with it. This method reduces the brightness of the lamp appreciably, since the triac drops about 1.5 V, which is more than 6% of the nominal lamp voltage. To compensate this loss, the mains voltage to the projector should be increased by that percentage. The transformer and ventilator can cope easily with that kind of increase, and so can any electronic circuits, since these are invariably powered via a regulator.