one who is thoroughly familiar with the performance of
93. Type M Resistors
the complete equipment.
a. Type M resistors are used in the circuits where
large resistor capacity is required. This resistor is built
c. At light and heavy inspections examine the
of tubular units having steel center supports insulated by
resistor panel carefully for loose connections. Take the
sections of porcelain. A resistance ribbon is wound
resistor tubes from the panel and check for broken or
edgewise in the form of a helix about the sections of
open circuited tubes. Care must be exercised in
porcelain. The units are mounted on insulated tie rods
replacing the tubes and making proper connections.
supported on a strap steel frame. Each unit may be
d. Replace broken or damaged tubes only with
removed easily without disturbing any of the other units.
tubes having identical style number.
b. The resistors limit the amount of current flow
through the respective circuits and thus have an
95. Switches and Fuses
important part in the overall performance of the
a. Inspect all hand switches and fuses (if used)
equipment. Electrical characteristics of the equipment
regularly, to cover:
can be upset by the adjustment of a resistor in an
(1) Switch jaws, fuses and fuse clips making
important circuit. All resistance values are properly
good contact.
adjusted when the unit is first put in service.
(2) Leads firmly soldered, terminals and bolts
Adjustments will only be made by one who is thoroughly
tight.
familiar with the performance of the complete
(3) Panels or bases clean, free from oil and
equipment.
dust.
c. At light and heavy inspections examine the
(4) Correct fuses in use, spare fuses
complete resistor assembly for broken porcelains and
available, and auxiliary apparatus tested if
resistance ribbons. Check that all connections are tight
one fuse blows frequently.
and properly made and that the resistance ribbon is
(5) Any springs correctly in place and
properly and securely clamped in the end terminals.
operating.
Clean the mounting insulators and frame terminal bar.
(6) Apparatus tested for proper operation.
d. At general overhauls, in addition to the above
inspections, tighten the mounting bolts and clean the
(7) Contacts clean and smooth.
insulating terminal bar, then paint with insulating
b. Cover in this inspection all items such as control
varnish.
and. miscellaneous switches and fuses, traction motor
e. When replacing a resistor tube, care should be
cutout switches, weight transfer and sander foot
taken to have the terminal clamps and resistor ribbon
switches, buttons for engine stop or other circuits,
clean, smooth and bright before making connections.
headlight hand switches and fan or traction blower
Use new terminal clamps when replacing tubes.
switches, and train line jumpers and receptacles.
94. Control Resistors
96. Voltage Regulator Panel
a. The control resistors, which carry only low
a. Description.
values of current, consist of resistance wire wound on
(1) This voltage regulator is of the vibrating
tubes. The tubes are of various ohmic values as
type. It varies the auxiliary generator
specified on figure 44.
shunt field currents to hold constant
b. The control resistors also have an important
voltage on the auxiliary circuits regardless
function in the overall operation of the electrical
of auxiliary load or engine speed.
apparatus. The characteristics of the equipment can be
(2) The regulator has a powerful magnetic
disturbed by changing the values of the control resistors
circuit which is excited by a single coil on
in important circuits. The resistors are properly adjusted
the stationary frame. The moving iron
when the equipment is first placed in service and should
armature is supported by a flat stainless
not be tampered with. Adjustment will be made only by
steel hinge spring which is spot welded to
the armature iron. The two arms of this
spring fit over dowel pins located in the
edge of the top plate of the stationary
frame. The spot-welding of the hinge
spring and the location of the
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