the opening and closing of the relay contact
control which automatically slides in place over
points.
the stop button after the button is depressed.
This prevents the varidrive assembly from
c. Negative and Positive Binding Posts. The
being started when accidentally pushing the
negative and positive binding posts (30-B) of
start button. This safety clip also holds the
the test indicator circuit are a two piece post
stop button in a partially depressed position
as described in paragraph 38d. The posts are
which places the circuit of the external ac power
used to connect the test indicator circuit to the
source to the test stand in an open condition.
relays undergoing test by means of two tested
This safety clip must be slid off the stop button
leads.
to close this circuit when performing tests that
do not require the use of the varidrive assembly
or to release the stop button when the start but-
nated as AC POWER ON)
ton is depressed to start the varidrive assembly.
The ac power-on indicator lamp (31) located
on the near center of the front panel above the
drive control (33), is connected to the external
nated as DRIVE RUNNING)
ac power source leading to the circuitry within
The drive running indicator lamp (34), lo-
the test stand and consists of a 125-volt dc lamp
cated on the near center of the front panel and
with a green lens. It provides a visual means
to the left of the ac power-on indicator lamp
to indicate that the external ac power source is
(31), is connected to the circuitry of the vari-
being supplied to the circuitry within the test
drive assembly and consists of a 125-volt dc
stand. This visual indication is detected when
lamp with a green lens. It provides a visual
the external ac power source is turned on and
means to indicate that the varidrive assembly
the switch on the circuit breaker (fig. 11) is in
is in operation.
the "ON" position.
(Designated as PILE FLUTTER JACK)
The speed control (32) located on the center
a. General. The pile flutter circuit consists
right hand side of the front panel, is a man-
of three units which are located on an instru-
ually operated mechanism used for varying the
ment panel (35) on the lower right hand end
speed of the generator or alternator being
toward the center of the main control panel.
tested, by turning the speed control handwheel
The circuit is used when adjusting the carbon
clockwise to increase the speed and counter-
pile of a generator (alternator) regulator of an
clockwise to decrease the speed. The numerals
ac/dc system and is used without the varidrive
on the speed control dial do not necessarily indi-
assembly operating (par. 43). The circuit is
cate the speed of the unit being tested, but it
connected to the contacts under the regulator
is used as a reference guide only. Any variation
cover leading to the carbon pile (cover is re-
in generator or alternator speed will be indi-
moved for access). An electrical headset (fig.
cated directly on the tachometer indicator meter
(3).
is used to listen for the vibration of the carbon
pile when adjusting it. A crackle in the ear-
43. Drive Control
phone or an erratic vibration indicates loose
The drive control (33) located on the near
adjustment of the carbon pile. No noise at all
center of the front panel and to the left of the
indicates too tight an adjustment of the carbon
speed control (32), is a 110-volt, 60 cycle, push-
pile. For a correct adjustment there should be
button type switch which is the manual oper-
a distinct even hum. The three units of this
ating device used to set the magnetic motor
circuit and their description and function are
starter (fig. 11) in action to start the varidrive
given in b and c below.
assembly of the test stand. Depressing the start
button (33-A) starts the varidrive assembly
b. Phone Jack. The phone jack (35-A) of
and depressing the stop button (33-C) stops the
the pile flutter circuit is an open circuit two
assembly. There is a safety clip (33-B) on the
conductor type jack which is used to plug the
