ampere load slowly by using the above
fixed load switches, and if necessary,
should go back to "0" and to the right
by placing the 0-25 0-12.5 load switch
(positive) to approximately 100 milli-
volts.
(12-D) in the "ON" position and
turning the variable load 0-25 0-12.5
( 9 ) Release the dc volts-millivolts mo-
a m p e r e rheostat (13) slowly clock-
m e n t a r y - o n switch (21, fig. 16). The
wise and observe a slight drop-off in
h i g h e s t dc millivolts reading on the
the regulator voltage on the dc volt-
dc volts-millivolts meter (4, fig. 16)
i s the differential voltage (see
a m p e r e reading on the load dc am-
above for specification for voltage
m e t e r (1), when the current regula-
setting).
( 1 0 ) Turn the 40-ohm field current rheo-
box goes into action.
stat (16) counterclockwise, very
(6) Place the fixed load switches (12-A)
slowly, to decrease the voltage reading
(12-B) and (12-D) in the "OFF"
o n the dc voltmeter (4), observing
p o s i t i o n and turn the rheostat (13)
the load dc ammeter (1). The current
fully counterclockwise. Continue with
reading on the meter should increase,
t h e differential voltage and reverse
t h e n indicate a reverse reading, and
c u r r e n t test for the differential and
then come back to "0" when the relay
r e v e r s e current relay in (7) below.
o p e n s . The maximum reverse current
Note. The starter test load disconnect
reading attained is the reverse current
switch (10) remains in the "ON" position
s e t t i n g for the differential and re-
f o r the following tests.
verse current relay assembly (see
(7) Place the 40-ohm 30 ampere maxi-
above for specifications for re-
mum rheo-reg switch (17) in the
v e r s e current setting). Turn off the
" R H E O " position, the load dc am-
battery switch (20).
m e t e r range selector switch in the
(11) Change the load dc ammeter range
"50A (X1)" position, and the dc
v o l t s - m i l l i v o l t s range selector switch
selector switch (5) to the 150A (X3)
p o s i t i o n . Place the 50-25 fixed load
(7) in the 900MV position. Turn the
switch (12-B) in the "ON" position
4 0 - o h m field current rheostat (16)
slowly clockwise until the voltage on
(be sure the starter test load discon-
nect switch (10) is in the "ON" posi-
volts below battery voltage (below 18
tion).
v o l t s ) , then place the battery switch
( 1 2 ) Hold the dc volts-millivolts momen-
(20) in the "ON" position.
t a r y - o n switch (21, fig. 16) up to
( 8 ) Hold the dc volts-millivolts momen-
" R E A D " position and note the milli-
volt drop reading across the contacts.
"READ" position and turn the 40-ohm
The millivolts drop should be approxi-
field current rheostat (16) further
m a t e l y 150 millivolts reading on the
clockwise very slowly, until approxi-
m a t e l y 18 volts are indicated on the
a n d the reading on the load dc am-
m e t e r (1) should be approximately
dc volts-millivolts meter (4, fig. 16)
48 amperes (refer to TM 9-8631).
should deflect to past "0" and to the
S t o p the varidrive assembly by de-
left (negative) side of the dial to ap-
p r e s s i n g the stop button (21-C) of
proximately 450 millivolts and as the
t h e drive control (21).
v o l t a g e reading on the dc voltmeter
( 1 3 ) Place the switches and controls in
(4) is increased to approximately 25
v o l t s by turning the rheostat (16)
of the table. Re-
dicated in column
f u r t h e r clockwise, the needle of the