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Model 7754A/7414A
tiometer setting permits front panel adjustment of the trace
density through the heat control circuit in each driver
amplifier (paragraph 4-21).
4-26. CHART DRIVE.
4-27. The recorder chart drive consists of a 115 volt ac
motor, a gearbox with four clutches and speed selection
solenoids, a pair of paper drive rollers, and a paper brake
, bar.
4-28.
Chart Motor.
4-29. The chart motor is a continuous duty, synchronous
motor with a speed of 450 rpm for 60 Hz operation. A
sprocket gear on the motor shaft engages a drive chain that
transmits power to the gearbox. To provide additional elec-
trical safety, the motor is insulated from the recorder
chassis by non-eonducting spacers and an insulated sprocket
gear at the gearbox input.
4-30. Speed
Control.
I
4-31. Chart paper speed is varied by a gear train consisting
of sets of four gears, on two shafts (Figure 4-7). These
Section IV
Principles of Operation
shafts are fixed in place and do not rotate. Each set of four
gears (A, B, C, and D) either provides a'
~peed
reduction
with all four gears transmitting power, or "no speed reduc-
tion, with power bypassing the reduction gears through a
spring clutch that links gears A and D on the primary shaft.
Gear D is machined together with Gear A of the next set, so
power is directly transmitted to the next set of gears.
4-32. When direct drive is desired, the associated solenoid is
energized, withdrawing the plunger from the clutch pawls.
The clutch then engages, coupling gears A and D. The
spring clutch between gears Band C automatically disen-
gages since output gear C, being smaller than input gear B,
rotates faster when gears A and D are in direct drive.
4-33. SPEED SELECTION SOLENOIDS. Solenoids Ll, L2,
L3 and L4 control the speed reduction. They are energized
from Control Switch Assembly A2Al. The paper speeds
obtained by energizing different combinations of solenoids
are presented in Figure 4-8. Remember that as more sole-
noids are energized, the fewer are the sets of gears that
provide speed reduction, and thus the paper goes faster.
4-34. POWER FLOW. The mechanical power flow through
the gearbox is diagrammed, for each speed, in Figure 4-8.
SECONDARY
SHAFT (FOR ALIGNMENT ONLY)
SPRING CLUTCH
ACTS SAME AS SPRAG-TYPE CLUTCH,
TO PERMIT OVERRIDING ACTION
WHEN SOLENOID IS ENERGIZED.
COIL
SPRING CLUTCH:
STRAIGHT THROUGH DRIVE
WHEN ENERGIZED SOLENOID
ALLOWS SLEEVE TO TURN
PRIMARY SHAFT
(FOR ALIGNMENT ONLY)
07754-1
Figure
4-7.
Chart Drive Gears
4-7
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