Lincoln Electric PRECISION TIG 375 Service Manual page 102

F-56
MOUNTING OF STUD TYPE DIODES TO ALUMINUM HEAT SINKS (CONT'D)
PROCEDURE
1. Loosen the appropriate diode nut and remove the
diode that is to be replaced.
2. 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.
3. Polish each heat sink's mounting surface using
NO. 000 fine steel wool. Wipe surface clean with a
lint free cloth or paper towel.
4. 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 mount-
ing surface.
5. Apply a thin (0.0003" to 0.0007") uniform layer of
E1868 (Dow Corning 340) heat sink compound to
the heat sink mounting surface.
a. Do not apply compound to diode stud or
mounting threads.
b. The diode threads must be clean and free of
defects so that the nut can be finger tightened
before applying torque. A "slip" type torque
wrench must be used to tighten the diode nut.
6. Tighten the diode nuts to the specifications in the
following table.
a. The nuts for diodes with steel studs are to be
started by hand and then torqued as per the
following table.
b. The nuts for diodes with copper studs are to
run on all the way by hand then torqued as per
the following table.
c. Turn a minimum of 1/2 turn more while
torquing per the table.
TROUBLESHOOTING & REPAIR
PRECISION TIG 375
DIODE STUD FOOT-
SIZE POUNDS
3/4 - 16 25-27
3/8 - 24 10±.5
1/4 - 28
F-56
INCH-
POUNDS
300-324
125+0/-5
22-25