Rockwell Automation 1336S_F_E_T_R Transistor,Thyristor (SCR) Replacement - Manual (Page 2)

2 Transistor and Thyristor (SCR) Replacement for 1336 PLUS, PLUS II, FORCE, IMPACT and REGEN Drives
Surface Preparation After removing the transistor or SCR modules from the drive, the heatsink
and replacement modules must be prepared using the following method to
ensure proper heat transfer and operation of the replacement components.
1. Remove all old heat transfer compound from the surface of the heatsink
using a tool such as a rubber spatula that will not mar the heatsink
surface. Remove any remaining residue with a soft cotton cloth and a
cleaning fluid such as Essex Cleaning Fluid, Brownell OS-3 by Dow
Corning Co. (Mineral spirits may also be used if Essex cleaning fluid is
not available).
2. Use a non-marring cleaning pad such as a Scotchbrite by 3M TM to
remove any oxidation from the face of the heatsink. DO NOT use steel
wool or sandpaper to clean the surface of the transistor/SCR baseplate or
the heatsink, as they could scratch or score the surface which will
impede heat transfer from the transistor to the heatsink.
3. Follow the oxidation removal with a final cleaning of both the heatsink
and the module baseplate with cleaning fluid and the soft cloth.
Important: Thermal compound must be applied immediately to both
surfaces as detailed in the following Installation section to
prevent oxidation from reoccurring.
If a cleaning agent other than Essex by Dow Corning is used, make certain it
leaves No residue on the heat transfer surfaces.
Installation Install the transistor or SCR module to the heatsink as follows:
1. Apply a liberal coating of thermal compound (AOS52022) to the
transistor or SCR module base plate using the 6 gram blister pack (part
number 196261) recommended in
Table A for your particular device.
2. Apply the thermal compound until the metal surface is no longer visible.
Do not allow any foreign particles or contamination to collect on the
thermal grease. The nominal thickness of the grease coating should be
about 0.005 inches or 0.127 millimeters.
3. Mount the transistor or SCR module on the heatsink, pressing and
rotating in a slight circular motion to better seat the transistor onto the
heatsink and distribute the grease more evenly.
4. Apply slight pressure and attempt to lift the module back off the
heatsink. If the module does not easily separate from the heatsink, the
thermal interface is correct. If the module easily separates from the
heatsink with no suction effect, this could be due to insufficient grease or
foreign particles on either the module base plate or the heatsink. Remove
foreign particles and/or apply more grease and reseat the module until it
is properly attached to the heatsink.