TM 5-6675-316-14
The collector lens and mirror assemblies are
f. Carriage stepping assembly.
mounted on a carriage which moves parallel to the paper plane. The carriage moves
along wayrods driven by a stepping motor/cable arrangement.
(1) When the stepper signal #1 is high, the Darlington pair Q7 is biased on.
This allows current to flow from ground through emitter resistor R6 and the motor
coil to the +26 V supply. When stepper signal #2 is high, the Darlington pair Q6 is
biased on. This allows current to flow from the -26 V supply through emitter
resistor R5 through the motor coil to ground.
When the stepper signal input is low, the Darlington pair Q6, Q7 is biased
current flows.
With the Darlington pair Q6 or Q7 on, current flows through R5 or R6 and,
flow increases, the voltage drop across R5 or R6 increases, reducing the
forward bias on the Darlington pair Q13 and the current flowing through the motor
coil. This effectively controls the coil current.
2-30
