TM 5-6675-319-14
(c) To restrict the movement of magnification drive and prevent
c o l l i s i o n o r o v e r r i d i n g o f t h r e a d s , m a g n i f i c a t i o n l i m i t s w i t c h e s a r e u s e d . T he
limit switches are operated by adjustable actuators mounted on the inversor drive
n u t .
(d) As the inversor nut moves upward, its actuator causes the roller
on the limit switch to close, stopping the upward movement of the inversor nut. The
lower magnification switch is open, enabling the magnification drive motor to be
r e v e r s e d.
Mechanical overload protection is provided by shear pin in the gear
reduction portion of the magnification drive motor.
( 2 ) M a g n i f i c a t i o n m o t o r c o n t r o l l e r .
(a) When the negative (-) switch on the MAG assembly is depressed, low
is present on pin 5 of IC1.
IC1 pin 9 output goes low, turning on Q2. This ener-
gizes K2.
K2 energized contacts applies L1 (115 V ac) to one side of K4, energizing
IC3, Q3 and bridge rectifier (D6 through 09) form a dc to dc converter. The
bridge rectifier output is applied to TB2 A1 and A2.
T h e d i r e c t i o n o f r o t a t i o n is
controlled by relay K4.
K4 feeds the armature power supply from TB2 + (positive)
through its lower contacts to TB2 pin A2.
The dc outputs from TB2 pins Al and A2
are applied to chassis TB1 pins 8 and 9 then to the dc motor armature. The dc motor
t u r n s l e f t .
This causes the easel to rise, reducing image size. The dc motor will
c o n t i n u e t o r u n 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 l i m i t s w i t c h i n t h e m o t o r c i r c u it
opens.
7-12
