TM 5-3431-225-15
Section VI. RANGE AND POLARITY SWITCH, CONTROL
RHEOSTAT, lNTENSITY SELECTOR RHEOSTAT, START
ADJUSTMENT RHEOSTAT, AND TIG-METALLIC SWITCH
(2) Install the top and sides on the weld-
ing machine (para 3-26).
a. Removal.
(1) Remove the welding machine top and
housing (para 3-26).
a. Removal.
(2) Remove t h e t w o c o n t r o l r e c t i f i e r s
(1) Remove the top and sides from the
mounted to the polarity and range switch bracket
welding machine (para 3-26).
(2) Refer to figure 4-4 and remove the
( 3 ) Remove the control rheostat (para
intensity rheostat.
b. Testing.
(4) Refer to figure 4-2 and remove the
(1) Connect an ohmmeter to the two outer
range and polarity switch assembly.
terminals of the rheostat and set the meter on
b. Installation.
RX1 scale. The reading should be 10,000 ohms.
(1) Refer to figure 4-2 and install the
If the reading is more or less than 10,000 ohms,
range and polarity switch assembly.
replace the rheostat.
(2) Install the control rheostat (para 4-18).
(2) Connect an ohmmeter to the center ter-
(3) Install the two control rectifiers to the
minal and either outside terminal of the rheostat.
bracket of the range and polarity switch assembly
Set the meter on the RX1 scale. Turn the rheostat
in either direction until it stops, then turn it in
(4) Install the top and sides on the welding
the opposite direction slowly and evenly until it
machine (para 3-26).
stops again. The indicator on the meter should
increase or decrease evenly according to the speed
4-18. Control Rheostat
in which the rheostat is turned. If the meter in-
a. Removal.
dicator does not function as described, replace
(1) Remove the top and sides from the
the rheostat.
welding machine (para 3-26).
(2) Refer to figure 4-3 and remove the
control rheostat.
c. Installation.
b. Testing.
(1) Refer to figure 4-4 and install the in-
(1) Connect an ohmmeter to the two outer
tensity rheostat.
terminals of the rheostat and set the meter on
(2) Install the top and sides on the weld-
RX1 scale. The reading should be 15 ohms. If
ing machine (para 3-26).
the reading is more or less than 15 ohms, replace
the rheostat.
(2) Connect an ohmmeter to the center ter-
minal and either outside terminal of the rheostat.
a. Removal.
Set the meter on the RX1 scale. Turn the rheostat
(1) Remove the top from the welding ma-
in either direction until it stops, then turn it in
chine (para 3-26).
the opposite direction slowly and evenly until it
(2) Refer to figure 4-5 and remove the
stops again. The indicator on the meter should
start adjustment rheostat.
increase or decrease evenly according to the speed
b. Testing.
in which the rheostat is turned. If the meter in-
(1) Connect an ohmmeter to the two outer
dicator does not function as described, replace
terminals of the rheostat and set the meter on
the rheostat.
RX1 scale. The reading should be 15 ohms. If
the reading is more or less than 15 ohms, replace
the rheostat.
c. Installation.
(2) Connect an ohmmeter to the center ter-
(1) Refer to figure 4-3 and install the con-
minal and either outside terminal of the rheostat.
trol rheostat.
Set the meter on the RX1 scale. Turn the rheostat
