TM 5-3431-207-15
Section V. CONTROLS AND INSTRUMENTS
b. Replacement.
Remove the old resistor by
41. General
disconnecting both leads. Replace with a new resistor
The Model LA-300 welding machine contains all the
by soldering both leads into their correct position.
controls and instruments necessary for the operation of
the unit. The controls and instruments should be
45. Job Selector and Remote Control
checked often to make sure they are operating properly.
Remove the backs from the job selector (fig. 3) and
42. Volt-Amp Meter
remote control (fig. 9). Remove the output wiring from
the job selector by disconnecting it from the terminals.
a. Inspection. If the volt-amp meter (fig. 3)
Remove the handle from the face of the job selector.
fails to operate properly an inspection should be made.
The job selector may now be removed by simply lifting it
The connecting terminals in back of the volt-amp meter
from the case.
should be checked first to make sure they are tight, and
are connected properly. Make an overall inspection of
46. Current Control
the meter for damage. If the meter can be suitably
repaired, it should be, otherwise it should be replaced.
Remove the current control (fig. 3) handle by
b. Removal. Remove the mounting screws which
removing the setscrew and pulling straight out. Remove
the dial plate by removing its attaching parts. The
hold the volt-amp meter to the control panel.
resistance tube and brush holder may now be removed
Disconnect the terminal contacts at the rear of the
by removing all their attaching parts. The reactor may
meter, by unscrewing the terminal screws and removing
now be removed by removing the screws, nuts, and
the leads. Lift the meter from the control panel and
lockwashers which hold it into place.
replace with a new one.
47. Circuit Breaker
43. Switches
Disconnect all electrical leads in back of circuit
If a switch (fig. 3) fails to operate properly, it
breaker (fig. 3). Remove the screws and nuts which
should be replaced at once. The switch is removed by
holds the breaker into position. The circuit breaker may
removing the mounting screws from the control panel, or
now be removed from the control panel and replaced
by simply removing the knob. In order to completely
with a new one.
free the switch from the unit, the terminal leads should
be removed from the switch. Lift the switch from the
48. Receptacle
unit and replace with a new one.
Disconnect terminals in back of receptacle (fig. 3).
44. Resistors
The receptacle can now be removed from the control
panel by removing the screws and nuts which hold it into
a. Testing. Connect the resistor leads to the tester
position.
and read the amount of resistance left in the resistor.
49. Terminal Board
Disconnect all leads from the terminal board.
Remove screws and nuts which holds the board.
Remove the terminal board.
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