TM 5-6675-320-14
(5) The squarewave output of U11 drives the ground-based transistor pair Q9
on the positive half-cycle and Q13 on the negative half-cycle. The transistor Q17
provides the necessary current gain to gate the FET Q25. The transistor Q18 pro-
vides inversion as well as gain for the FET Q26.
T h e F E T s w i t c h i n g a c t i o n p r o v i d e s
the current required to microstep the plotter motor.
aj. Power supply assembly.
The power supply consists of three PCAs, a rear panel,
and the power transformer, which is mounted in the lower case assembly.
ak.
P r i m a r y C i r c u i t s.
The ac line input connection is through the receptacle
mounted on the rear panel.
The ac line fuse holder is also mounted here. From the
rear panel, the ac input is wired to the primary PCA A5. Mounted on this PCA are
the broad band line filters L1 and L2, the LINE switch S1, and the voltage selection
jumpers W1-W3.
These jumpers are inserted in sockets to match the plotter primary
c i r c u i t s t o o n e o f f o u r a c l i n e v o l t a g e s.
Jack J1 connects the primary PCA with the
primary side of the power transformer T1.
The secondary of the transformer is
connected through J5 to the filter and rectifier circuits of the power supply PCA
A4. This rectifier circuit supplies the plus and minus 34 volts which supplies the
main power supply and the X- and Y-motors.
Table 4-17. POWER SUPPLY OUTPUTS
Supply
Type
Use
±34 V
Zener regulated and balanced
Motor driver and power
s u p p l y c i r c u i ts
+5 V ref
Zener regulated
Power supply reference,
reset, and chart hold
+12 V aux
Zener regulated
Power supply operation
+5 V
Regulated switching supply
P l o t t e r o p e r a t i n g
+12 V
Regulated switching supply
P l o t t e r o p e r a t i n g
+46 V
Zener regulated
+FET gate supply
-22 V
Zener regulated
-FET gate supply
-12 V
Zener regulated
P l o t t e r o p e r a t i ng
voltage
voltage
voltage
±12 V
I n t e r l o c k ed
Motor driver and balance
circuit shutdown
a l .
Reference supply.
The +34 volt main power is the source for the reference
supply which controls all other power supply voltages. This Zener-regulated supply
produces a +5 volt reference and a +12 volt auxiliary supply. These voltages come
up first and are used to control the switching supplies, balance circuit, and the
2 0 k H z o s c i l l a t o r c i r c u i t.
4-134
