BUILDING YOUR own sound system can be an exercise in Zen patience or total frustration. But there are some concrete reasons for giving kit building a try. The money you can save is pretty gratifying, for instance. A Dyna FM-5 tuner, which sells for $319 factory-wired, costs only $199 in kit form. What’s more, if something conks out, you can usually fix kit-built units yourself, rather than getting scalped by a serviceman who had to wait two months for parts from Japan.
So why doesn’t everyone roll their own stereo? Fear, mostly. Many are stopped by the idea that you have to know something about electronics before you can successfully assemble the hundreds of parts in a typical receiver. This simply isn’t true. Modern kits are so “idiot proof” and their manuals are so profusely illustrated, that knowing the difference between a volt and a vacuum cleaner is all the theory needed. If you’re dealing with the established kit companies (Heath and Dynaco are the best known, Southwest Technical Products and Ace Audio are more recent entrants into the field) the task is purely mechanical.
I once taught a group of ten-year-olds to solder — it took about five minutes per child. All of them were then able to build their own transistor radios. If you have normal physical dexterity, your only worry might be colorblindness, which would disqualify you, since the most common parts (resistors and even wires) are identified only by color.
The other big concern is whether kit-built units work as well as factory-built ones. While many electronic circuit designs don’t lend themselves to kits, there’s nothing inherently inferior about designs that do. Critical portions of the kit that require instrument alignment come as prewired and adjusted subunits. As for the home-built parts, it’s always possible to get a defective transistor or to make a wiring mistake that a factory quality-control section would spot. But the resulting problem(s) are usually obvious and relatively easy to track down and correct.
To get started in kit construction you need remarkably few tools. A low-wattage (25 to 50 watts) soldering iron with a small (about 1/8″) tip is a must. Ungar or Weller “soldering pencils” are the best known, but any brand will do. Don’t get a bigger iron or “gun”; its high temperatures will burn out delicate solid-state components faster than you can solder with it. A pair of needle-nose pliers (five inches is the normal size) is also essential; you can save the cost of another tool, a pair of diagonal cutters (or “dikes”), if you get pliers with a wire cutter close to the tips so you can use it to trim excess wire protruding through printed circuit boards. An inexpensive wire stripper is also a necessity, along with a screwdriver (a 1/4″ blade will handle almost all the screws you’re likely to encounter, but occasionally you may need the thinner 1/8″ size). Allow plenty of space — a card table protected by an old beach towel is usually about right. While the box of parts may be small, and the finished product smaller still, at the start you’ll have to spread out (and find) a seemingly infinite number of parts. Muffin trays make handy containers for hardware and small parts, and the corrugated edges of the packing box are ideal for resistors and capacitors.
Make sure you check the contents of your kit against the parts list. Kit manufacturers are careful to include everything, but if anything is missing, this is the best time to find out. Otherwise, for instance, you could come to the step on page six that says to wire the 510-ohm resistor (green-brown-brown color bands) from lug 3 to lug 6 of switch AA, as shown in Pictorial 1-4, and find that you used it two pages earlier on the printed circuit board, where one of several 150-ohm resistors (brown-green-brown bands) was called for. If you check the parts list, you can avoid backtracking.
Patience and prudence aside, 90% of kit-building troubles come from improperly soldered connections. Good soldering technique is a simple, easily acquired skill:
1. The tip of the iron should be clean and, when hot, shine brightly from a thin coating of molten solder. A damp sponge is the handiest way to wipe off the crud that eventually builds up. A little solder melted directly on the tip from time to time will keep the iron well “tinned.” Most kits supply some solder. If you have to buy more, make sure it’s 60/40 rosin core — 1/16″ or less.
2. When soldering a connection, heat the wire(s) with the iron to one side, while feeding the solder against the opposite side of the wire(s). That way, the work itself will heat the solder enough to make it flow. Don’t melt the solder against the iron, expecting it to flow onto the part you want joined. If you do this, most of the flux in the solder will boil off before it reaches the part, and you’ll never be sure that the work itself got hot enough to make the solder stick to it.
The solder will set within a few seconds and should have a smooth (not grainy) appearance. Where two surfaces have been joined, the solder bond between them should be concave rather than convex.
3. If the completed joint has a dull and grainy look, you’ve probably made a “cold solder joint.” If this happens, simply reheat the joint and add a bit more solder. Don’t leave cold solder joints alone just because they seem firm; electrically, you may be getting no contact at all.
4. Before installing a resistor, capacitor or diode, clean its leads by scraping them with a pen-knife or a piece of medium-grit sandpaper until they are shiny. Wax, dirt, oil and oxidation on the wire leads keep the solder from “wetting” them, again resulting in poor connections.
5. Don’t use too much heat. Excess heat can destroy nearly any component, particularly solid-state parts (diodes and transistors). It’s a good idea to place a heat sink (an alligator clip or simply the tips of your pliers if you can get someone to lend a third hand) between the body of your device and the point where heat will be applied.
With a little practice, you’ll be soldering like a pro, although it would be foolish to take on something as complex as a receiver or color TV as your first kit. Just about any kit will give you enough practice, however. And when it plays the first time you plug it in, it won’t be the only thing turned on.