Attaching the Power Devices
In this build the two regulators are insulated from the panel with soft red insulating pads.
The RPSU PCB needs to be fitted to your case metalwork. Use the PCB as a template for the four
holes needed for the mounting pillars. The board should be spaced high enough off the panel so as
to not short out any of the components' leads should the board be flexed downward. However, they
should also not be too long so that the leads from the two regulators can't reach through the board to
be soldered. I find an 5 or 6mm spacer works very well.
Now you need to prepare the leads of the two power devices. The three legs need to be bent
upwards so that the PCB can be fitted over them. Note that the top surface of the device is marked
with the name of the component and it is the flat side on the bottom of the device that will be in
contact with the panel. You should be able to see that the leads have a thicker section close to the
body of the device. Make a 90 degree bend upwards at the point where the lead thickness changes.
Do this for all three legs of the device.
Remove the board from the panel and fit the power devices to the board by poking their legs up
through the bottom of the board. Do not solder them but fit the board back into place. Use the hole
in each regulator to mark out where you need to drill the mounting hole for the two devices. Now
remove the board and regulators. Carefully drill a 3.8 or 4mm hole in the panel for each of the
regulators. Clear off any swarf and, twisting with your hand only, use an 8mm drill bit to lightly
deburr the edges of the holes. There should be no bumps around the holes.
The regulators are both TO-220 devices. They both need to be fitted to the panel mechanically and
thermally but not electrically. That is the metal tab on each device that will be mounted to the panel
should not make electrical contact with the metal panel. To achieve both thermal transfer and
electrical insulation we use an insulator. These can be made of a 'soft' flexible material in the form
of an insulating pad or a rigid thin glass like plate made from mica. If using the mica you will also
need to use heat transfer paste. Since the paste is somewhat messy I recommend you use the
insulating pads. Both types are normally available in 'mounting kits'. Also in the kit is a mounting
bush. This top hat shaped piece of stiff plastic prevents the mounting screw from touching the
regulator's metal tab.
