Elecraft KPA500 Kit Assembly Manual - Manual (Page 14)

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Use your DMM to verify the tab of U3 is insulated from the heat spreader and the mounting screw. The
resistance is typically greater than 5,000 ohms if the tab of U3 is properly insulated. A short would be indicated
by a very low resistance, close to what your DMM indicates when the test leads are touched directly together. If
you find a short, inspect your installation carefully and correct the problem. If the thermal insulator is installed
correctly, it will prevent any contact between the metal tab on U3 and the head spreader. If the shoulder washer
is installed correctly, the shoulder will center the screw in the hole in the tab on U3 so it passes through without
touching it, and the washer keeps the screw head and lock washer from touching the tab.
After you have confirmed there is no short between the metal tab on U3 and the head spreader, carefully
bend the heat spreader and integrated circuits back to vertical.
Mount the power supply module on the bottom cover as shown in Figure 11. Be sure to install all seven
screws and washers in the locations shown by the arrows in the figure. Note that one of the screws threads into a
2D fastener you installed at the corner earlier.
Figure 11. Mounting the Power Supply Module on the Bottom Cover.