TM 5-6675-320-14
b . P e n s o l e n o i d.
Controls the up/down position of each pen. The controlling
signal to the pen solenoid may originate from either PCA A3 or PCA A5. The pen up
or pen down signal from either the processor or the front panel is coupled through
connector J5-7 to the base of input transistor Q17. A low (0 V) pen down signal
turns transistor Q17 causing a positive input to the inverting input of current
a m p l i f i e r U 3 - 2.
The negative output of U3-6 turns on transistors Q18 and Q19 via
diode CR4.
Conduction of Q18 provides a current path from the -12 V supply through
connectors J1 and J2, pin 8, to energize the pen solenoid which is mounted on the
p l o t t e r a r m.
From there, the current travels through the pen solenoid to connectors
J1 and J2, pin 7, and then through transistor Q18 to common. Diode CR4 provides
protection for transistors Q18 and Q19 when the pen is up. A positive pen up signal
keeps transistors Q17 and Q18 in a nonconducting state, so the pen solenoid is not
energized and the pen remains in an up position.
c .
Transistor driver PCA Card A12.
Boosts an analog position signal from
interpolator to drive the X- and Y-drive motors.
The analog position signal is
interfaced by X14 drive amplifiers.
PCA A12 is mounted adjacent to the stepping
motors on the underside of the upper deck assembly and houses the eight motor drive
p o w e r t r a n s i s t o r s.
These eight motor drive power transistors provide current to the
X- and Y-drive motor windings, utilizing the ±26 V supply from the pen relay drive
c i r c u i t s .
The eight transistors are in pairs, one NPN and one PNP, so each of the
four motor phase windings has two transistors connected in a push-pull arrangement
t o p r o v i d e i t s d r i v e c u r r e n t.
d. X- and Y-axis drive motors.
Drive and control the movement of the plotter
arm and thus, the chart pen.
The operation of both X- and Y-motors is identical.
If the X-sine phase winding is activated, then PCA A8 outputs a signal through
connector J1-6 which is coupled through connector J1-2 to common the bases of tran-
sistors Q5 and Q6.
I f t h e s t a t e o f i n p u t s i g n a l i s p o s i t i v e , t r a n s i s t o r Q 6 w i ll
conduct, energizing that motor winding which is in common with the emitter circuit.
I f t h e i n p u t s i g n a l i s n e g a t i v e , t h e n t r a n s i s t o r Q 5 w i l l c o n d u c t , e n e r g i z i n g t h e
motor winding in a reverse direction.
The stepping X- and Y-drive motors are iden-
t i c a l .
Each has 1.8-degree steps making 200 steps per 360-degree rotation. Motor
rotation is translated into movement of plotter arm through the drive wire system.
4-3.2.6 Power SU p p IY .
Provides an electrostatic chart hold voltage and dc
supply voltages as shown below:
For power supply control only: +8 V, +5 V, +12 V
For plotter circuitry: +7 V, +5 V, +12 V, -12 V, +26 V, -26 V
The power supply consists of the following PCA cards:
Main power PCA card A9
Control PCA card A10
Power distribution PCA card A11
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