■ FIGURE 3. Internals.
the box. This extra length also gave protection to the low
voltage power supply (located at the lower left in
Figure 3). I then laid out and machined openings for
the fuse, power switch, and panel meters, which required
rectangular holes (approx 1” x 3”).
For any particular panel meter, first scribe out required
rectangular openings on the front panel and then “hog”
out as much material as you can with a large drill bit.
Then clamp in a vise and clean up the rest with a file.
By clamping a straight piece of wood in with it and lining
it up with the layout line, you give yourself a nice filing
guide. Better yet, use a hand nibbler tool. I have used one
of these and for the price, it’s not a bad deal. I’ve included
a part number for this in the Parts List.
The low voltage power supply is simple, and should
remain trouble-free for a long time. There’s a technique I
use that I’ve become fond of lately. Construct this on a
piece of Formica laminate of the proper size (2-3/4” x 2”
for mine). Lay out where the components will be and
drill 1/16” or smaller holes for their leads. Push them
through and connect the pigtail leads point-to-point
and solder them up. Use solid #22 insulated wire for
crossovers or longer runs. Epoxy the transformer in place
and connect it up.
The whole assembly is mounted with two 6-32 bolts
that are inserted through the drilled holes in the bottom of
the box and the previously glued laminate on the inside
bottom of the box. Nut these down to help hold the
insulator in place (these nuts will also serve as board
standoffs). Next, drop the board with matching holes onto
these protruding screws and nut it down. I actually drilled
these holes all at the same time by clamping all three
pieces together in proper alignment and then drilling. (This
was all done prior to the board component mounting, of
course.) I like this method because it is cheap and simple,
■ FIGURE 4. Term