TM 5-6675-323-14
b. The 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 SCR's are triggered by the action of the remaining components on
t h e b o a r d . N o r m a l l y , the SCR's prevent all of each ac half-wave from being trans-
ferred, 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.
4-4
