TM5-6675-326-14
2 – 3 . 2 . 1 I l l u m i n a t i o n – C o n t i n u ed
When the trigger diode reaches the breakover voltage of 43 ±5 V , it
conducts to complete the path across rectifier bridge CR1.
This forms a
closed loop circuit through capacitor C2,
the primary of pulse transformer
T1, and rectifier CR1, and current flows until capacitor C2 is discharged.
The discharge time is very fast and a short duration pulse is generated,
shaped by capacitor C3.
The pulse current flowing through the primary of pulse transformer T1
induces a voltage across the appropriate secondary, which is applied
through diode CR3 or CR4 to the gates of SCR Q2 or Q1, respectively. When
either SCR is triggered, it allows the rest of the ac half-wave to pass to
the external grid lamp transformer 1T1 through pin B.
The SCR will
continue to conduct until the ac half-wave reaches the zero crossing
p o i n t , a t w h i c h t i m e i t t u r n s o f f.
2 – 3 . 2 . 2 C l u t c h C o n t r o l.
X- and Y–axes manual motion controls are
connected through electrically operated clutches to chain drives.
Power
to the clutches may be interrupted to decouple chain drives and permit
rapid movement of the optical mount in the X- and Y–axes.
Current (120 v, 50/60 Hz) is stepped
transformer,
r e c t i f i e d i n p r i n t e d c i r c u it
down to 12.6 vac in the
assembly (PCA) A4 to 12 vdc.
Current passes through the quick-disconnect and brushes to the
quick-disconnect and clutch power switch.
The momentary switch on the
optical carriage is normally on , except when pressed by the operator.
Twelve vdc passes through the brushes to the series-connected clutches.
Note that the quick-disconnect separates the Y-axis clutch from the
c i r c u i t .
2-7
