Hey Vanilla Ice,
It was tough going because I was first out of the chute. I'll send Bob McRee an e-mail asking for clarifications on the design regarding some details about the main regular circuit. I built the power supply in stages that I could test easily. If you do that, the build goes smoothly and is less intimidating. Here is how I proceeded:
(1) Figured out how to mount transformer securely to a flat surface (i.e. bottom panel of instrument case).
I got a piece of angled aluminum from Lowes, cut two lengths from it the width of the transformer, notched out the center of one side of both angled pieces so they would clear the transformer windings, then drilled holes at each end of the notched side to match two holes located near the bottom of the transformer. I got four #10 1-3/4" nylon screws and #10 nuts from a local RC hobby store. Two were used to hold the angled brackets on the transformer, and the remaining two were used in the remaining two holes near the top of the transformer to keep the laminations from separating over time. I drilled the holes in the angle brackets so that when the assembly is mounted on a flat surface, the transformer rests slightly above the surface preventing the bottom edge of the laminations from touching the surface.
(2) Figured out the minimum dimensions that case would need to have and bought one.
The transformer is the tallest item that goes in the case. With the aluminum brackets attached, it would need to be at least 3-1/4" tall in order to keep the top of the transformer from touching the top of the case. I estimated that I would need at least 5" inches in width to have room to place the fuse and IEC power connector beside the transformer inside. I also estimated that I would need at least 6" in depth to have room for the large rectifier bridge, circuit board, and room for front panel connections. I ended up using a 4" high x 11" wide x 8" deep case which gave me plenty of room inside. More room for components meant more separation between components and less worry about heat buildup.
(3) Figured out where each panel-mounted component would go and cut all the necessary holes.
I first made thin cardboard templates of the front and back panels and cut holes in the templates where the components would go. There is nothing critical about where the panel-mounted components go, but it makes sense to put the power outlet and fuse on the back and everything else in front. I then held the cardboard templates on the panels and drew the hole outlines on the panel with a small magic marker. I then drilled all the round holes in the panels starting with small bit sizes and increasing the size slowly until the hole sizes were correct for the items to be mounted. Finally, I drilled a large round hole centered within each area that was to have a rectangular cutout, and used a metal nipper tool to cut from the hole to the edges of each rectangular cutout. The IEC power outlet cutout was easy. The front panel cutout for the display required the tightest tolerance and took a bit of time. I chose to add a cutout on the back panel for an AC power rocker switch that I purchased from Mouser.
Since I used a metal case, I also drilled a hole below the IEC receptacle cutout for attaching a short ground lead from case to the IEC receptacle ground.
(4) Determined how and where I would mount the transformer, large rectifier bridge, and circuit board(s) on the bottom panel and drill holes
I picked locations on the bottom panel where the transformer and large rectifier bridge would go and marked them on the panel. I decided that I would mount the tiny rectifier bridge for the display panel on its own prototyping board. I picked up a solderable prototyping board at rat shack. I also got some nylon spacers from Lowes and some small diameter, long nylon screws and nuts at the RC hobby store for mounting the protyping board and main regular board on the bottom panel. I placed these boards on the bottom panel and marked their mounting holes on the bottom panel. I then drilled holes in the bottom panel for mounting all of the above items.
(5) Assembled unregulated main supply components.
I started by soldering two lengths of striped wire to the transformer output windings for the main supply. I then mounted the fuse holder and IEC power receptacle on the back of the case and the transformer and main rectifier bridge to the floor of the case. I used thermal grease purchased at rat shack on the bottom of the rectifier bridge. I then wired the fuse, receptacle, and transformer input windings (black and white leads) together. I then ran the striped transformer output leads to the rectifier bridge. The keyed lead on the bridge is the + out. Its opposite corner is - out, and the remaining two leads are AC in.
I then installed the fuse, plugged in the power, and measured the main rectifier output.
Woo-hoo!! so far so good. No burning smell and nice positive voltage out of the rectifier.
If you would like me to continue with this build description let me know. Otherwise I'll assume that I've bored everyone silly and should stop.
-- Joey in Albuquerque.
