Troubleshooting & repair – Lincoln Electric IDEALARC R3R-500 User Manual
Page 87
TROUBLESHOOTING & REPAIR
F-53
F-53
IDEALARC R3R
PROCEDURE
1.
Remove the main input supply power to the
machine.
2.
With the 5/16” nut driver, remove the case
top and sides.
3.
Loosen the appropriate diode nut and
remove the diode that is to be replaced.
4.
Clean the area on the heat sink around the
diode mounting surface using a putty knife
or similar tool. DO NOT SCRATCH THE
DIODE MOUNTING SURFACE.
5.
Polish each heat sink’s mounting surface
using No. 000 fine steel wool. Wipe the sur-
face clean with a lint-free cloth or paper
towel.
6.
Inspect the mounting surfaces of each new
diode. Remove all burrs and wipe clean. Do
not use steel wool or any abrasive cleanser
on the diode mounting surface.
7.
Apply a thin (0.003” to 0.007”) uniform layer
of E1868 (Dow Corning 340) heat sink com-
pound to the heat sink mounting surface.
a.
Do not apply compound to the diode
stud or mounting threads.
b.
The diode threads must be clean and
free of defects so that the nut can be fin-
ger tightened before applying torque. A
“slip” type torque wrench must be used
to tighten the diode nut.
8.
Tighten the diode nuts to the specifications
in the following table.
a.
Start the nuts for diodes with steel studs
by hand and then torque them accord-
ing to the following table.
b.
Run the nuts for diodes with copper
studs on all the way by hand then torque
them according to the following table.
c.
Turn the nuts a minimum of 1/2 turn
more while torquing.
9.
Install the case top and sides.
DIODE STUD
FOOT-
INCH-
SIZE
POUNDS
POUNDS
3/4-16
25-27
300-324
3/8-24
10±.5
125+0/-5
1/4-28
22-25
MOUNTING OF STUD TYPE DIODES TO ALUMINUM
HEAT SINKS (continued)