the test stand, start the varidrive assembly as
of speed control (32, fig. 16) until 2000 revolu-
tions per minute are indicated on the tachom-
eter indicator meter (3, fig 16). Test the
tachometer indicator circuitry by checking the
s p e e d of the shaft of either driving head (4
and 5, fig. 7), utilizing a hand tachometer or
strobotac of known accuracy. If the reading on
w i l l need recalibrating. This may be accom-
plished by adjusting the potentiometer located
on a vertical plate behind the control panel (fig.
To obtain access
to the potentiometer re-
Location of the tachometer indicator circuit
move the six round head machine screws from
the panel, and lift the panel up and out to length
of nylon cords, using the lift handles under the
the voltage rating corresponding to the system
m e t e r s (fig. 16). Adjust the potentiometer by
loosening the locknut on the adjusting screw of
Caution: During any test procedures, do not
screw either clockwise or counterclockwise until
rotate the voltage selector switch (41-A, fig.
the reading on the instrument used for checking
16) as this will cause damage to the compo-
a n d the reading on the tachometer indicator
nents within the test stand as well as the equip-
meter are identical. Upon completion of the ad-
ment being tested.
j u s t m e n t , tighten the locknut and replace the
c. Before the start of any test, position the
control panel in the original position.
p o l a r i t y reversing switch (50, fig. 16) as re-
W a r n i n g : Disconnect the external power
quired for the type of electrical system under-
supply from the test stand and place the on-
going test (par. 100).
off input power toggle switch on the circuit
breaker (fig. 11) in the "OFF" position before
any attempt is made to lower the control panel
for access to the potentiometer.
a. P l a c e t h e O N - O F F i n p u t p o w e r t o g g l e
Caution: Do not move the handle of the
s w i t c h on the circuit breaker (fig. 11) in the
speed control (32, fig. 16) when the varidrive
"ON" position. Be sure to close the high voltage
assembly is not operating, also, before stop-
compartment access door (fig. 6) tightly or the
p i n g the varidrive assembly always reduce
interlock switch (fig. 12) on the compartment
speed to one-quarter setting.
may keep the input circuit open preventing the
v a r i d r i v e assembly from operating.
c. Check the storage batteries following pro-
cedures specified in TM 9-6140-200-15.
b. To start the varidrive assembly, slide the
safety clip (33-B, fig. 16) to the left and off
the "STOP" button (33-C, fig. 16) of the drive
a. Turn all range selector switches beneath
c o n t r o l . Depress the "START" button (33-A,
t h e meters on the test stand (fig. 16) to the
on the drive control and hold the button
m a x i m u m position, all rheostats counterclock-
closed long enough until the varidrive assembly
wise, and all toggle switches to the "OFF" po-
comes up to speed at which time the interlock
o f the magnetic motor starter (fig. 11) will
function and hold the starting contacts of the
b. Prior to performing any tests, position
starter closed. Holding the button closed should
t h e voltage selector switch (41-A, fig. 16) to