(c) To restrict the movement of the easel and lens drive, and prevent
c o l l i s i o n a n d o v e r r i d i n g o f t h e t h r e a d s , l i m i t s w i t c h e s a r e e m p l o y e d . T h e t i lt
limit switches are located on the left side of the base assembly. The easel limit
s w i t c h e s a r e l o c a t e d a t t h e r e a r o f t h e l e f t s i d e o f t h e r e c t i f i e r .
The inversor
limit switches are also located on the left side of the instrument. As the angle of
the easel increases, an actuator mounted on the easel pivot coupling causes the
easel switches to activate, stopping the tilt and magnification drive motors from
f u r t h e r i n c r e a s i n g t h e t i l t a n g ; e o r m a g n i f i c a t i o n . T h e t i l t l i m i t s w i t c h e s h a ve
t h e i r a c t u a t o r s m o u n t e d o n t h e t i l t d r i v e n u t.
As the tilt drive nut moves along
t h e t i l t s p i n d l e , i t s a c t u a t o r c a u s e s t h e l i m i t s w i t c h t o c l o s e , s t o p p i n g t h e t i lt
motor.
The direction of movement can be reversed. The inversor limit switches
limit the maximum and minimum magnification.
( 4 ) T i l t m o t o r c o n t r o l l e r.
(a) When the positive (+) switch on the TILT assembly is depressed, a
low is felt on pin 6 and pin 10 of IC1. Q1’s conduction causes relay K1 to ener-
g i z e .
The contacts of K1 apply L1 (115 V ac) to one side of K3, energizing it. The
dc to dc converter output is applied to TB2 Al and A2. The direction of rotation is
controlled by relay K3.
K3 feeds the armature power supply from TB2 + (positive)
through its lower contacts to TB2A1.
The dc output from TB2 pins A1 and A2 is
a p p l i e d t o c h a s s i s T B 1 p i n 8 a n d 9 t h e n t o t h e d c m o t o r a r m a t u r e . T h e d c m o t or
t u r n s r i g h t , i n c r e a s i n g t i l t u n t i l t h e + s w i t c h i s r e l e a s e d o r u n t i l t h e r e a r t i lt
or easel limit switches open.
7-16
TM 5-6675-319-14
