TM 5-6675-323-14
b. Ac voltage enters the dimmer circuit board through pin A and is trans-
f e r r e d to pin B through SCR Q1 or Q2, which determines the amount of the ac sine
wave voltage that is applied to the external high voltage transformer to light the
g r i d l a m p . T h e SCRS are triggered by the action of the remaining components on the
board.
Normally the SCRS prevent all of each ac half-wave from being transferred,
but when triggered, allow current to flow during the remaining portion of each half
sine wave until the zero crossing point is reached, whereupon the SCR is turned off
and the ac waveform is again blocked.
5-6
