Where to find parts
Controls, hardware & cases, etc. I bought the miniature pots, phone jacks, battery holder and
Carling DPDT switch from
Mouser. The surplus case, part #68429, came from Fair Radio Sales. Mouser has better cases for not much more. Yet the
Fair Radio case has a lot of room. Extra room is a very nice advantage. With a steel angle bracket. I
stiffened the plate aluminum top of the case. The sides of the case are cast aluminum, and very
sturdy. (Also, inside the case is an 1960s-era RF board. On this board are vintage transistors.
These devices might be germanium. I didn't test them.) In a
Radio Shack closeout sale, I found the nice fuzz and volume knobs. If I remember right, the
epoxy paint and ink jet decal material came from
Menard's. Also check office-supply stores. By the way, you can get similar decal material
for laser printers.
Decal art. The Fair Radio case is long and skinny. I like the shape. On top of this case, I
mounted one big decal. You can download and print my decal art. (For insurance, you might print two or
three copies of the art on the same decal sheet.) If necessary, cut up the decal so that the lettering
fits your fuzzbox. I found that large decals tend to wrinkle and trap air. Smaller pieces should stick
on more smoothly. Be sure that the painted surface is smooth.
Click to download decal art.
Low-gain transistors
Can't find low-gain transistors? Follow up on these ideas...
- Use power devices. Your case will be a little larger, but the circuit should work.
You can get a TO-220 version of the 2N3055 (TIP3055). In this circuit, this device
would operate electrically. The TIP31 is another possibility. You be the judge of the
tone these devices produce. I haven't tried them. Go to
Radio Shack's transistor page.
- Find a local hamfest and attend it. Look for those bags or bottles of old transistors. Do you
really think that "nobody has old transistors?" Never say die! Mine for your gold: Look
under the vendor tables. That's where vendors stash a lot of slow-moving junk. Try buying
an old radio, cassette recorder or stereo. You can harvest the parts. If possible, test parts
before using them. Be careful not to use a PNP transistor in this circuit. At the hamfest, don't
just try the commercial vendors. Check out the mom-and-pop cardtables in the outlying areas.
These tables have the one-of-a-kind items.
- Can't find a hamfest? Don't know where to look? Try here.
- Try other vendors. SMC
Electronics carries a lot of miscellaneous transistors. I also like
Electronics Goldmine.
Mouser, Digi-Key and
Allied offer datasheets for many devices. (Allied, Digikey and Mouser also offer the
wholesale price, often 10 percent of Radio Shack's price.)
Antique Electronic Supply (AES) sells transistors, passive parts, knobs, chassis, etc.
- I want to use Radio Shack parts. Okay, so you're a spoilsport. Be that way. I don't
know what you're doing about the case and Carling switch. Radio Shack doesn't stock those items.
Still, if you're creative, you can think your way through those problems. Radio Shack's
small-signal transistors such as the 2N3904 and 2N2222A have a gain of about 200. I'll tell you
a secret: By making easy circuit changes, you can reduce this gain to a reasonable value. See the
Troubleshooting & Mods Table.
- About gain. Before buying transistors, check the datasheet and find the device
hFE (beta). Beta is the current gain figure. If you want to match the original Dallas
Arbiter fuzzbox, look for a beta around 100. As I said, Dallas Arbiter's germanium transistors had gains of 70 and
120. Remember that the datasheet only gives typical values. Beta varies with applied voltage and
current. For example, the datasheet might provide beta at five volts and 100 mA. Yet you might be
using the device at nine volts and 136 μA. You'll also learn that individual transistors vary
within the spec. For this reason, a beta tester might show a more accurate value than the
datasheet does. Still, the tester is a far cry from your actual circuit. Also, some beta testers
inflate the beta by as much as 100 percent. Besides, beta also varies during operation. Variance
during operation is one reason for dynamic vs. static beta readings. Confused? Check the datasheet, and
consider the beta spec as a ballpark figure.
Carling switch
Carling seems to have the fuzzbox switch market locked
up. Both Digi-Key and Mouser
sell the product. The switch is good, but it's expensive. Why not? This is a super sturdy,
roadie-proof, reliable product, and nobody else makes it. The company manufactures in Mexico.
Viva Carling!
Assembly tips
The case is the chassis for controls and other parts. Mount the two pots on
the case. With short leads, connect these parts to the PC board. On either the input or output jack,
connect the ground to the ground tab. The input is a stereo jack. Your mono guitar plug grounds the
jack ring, connecting battery negative to ground. When you plug in the guitar, on comes the fuzz. Ready
or not!
Jacks. I recommend mounting the input and output jacks on the long sides of the case. The cast aluminum is
surprisingly easy to work. Before drilling, be sure that your jack threads run deep enough for the
case sidewalls. Mouser carries thick-panel jacks, but these jacks are expensive.
Battery. My battery mounts to a sturdy, metal clip on top of the case. That mounting makes
replacement easy. More important, a battery on the outside keeps the curious but electronically
challenged out of the case.
Template. As I said, I built the circuit on perfboard. I used the schematic as a template.
This template idea is key to successful perfboard construction. In a simple project like this effect,
your component order and placement should follow the schematic. Then you can easily check your circuit
against the schematic. Perfboard allows instant gratification, because you don't have to wait until you
get an etched board. The resulting circuit is as reliable as an etched version. Plus, changes are
easy and don't require a new board or messy cuts and jumps.
Here are the basics of perfboard prototyping...
- Bus wiring. Make the board look like the schematic. Just as on
the schematic, run a power bus across the top of the circuit. Run a ground
bus across the bottom of the circuit. Viewing from the top of the board,
parts should start with transistor Q1 on the left and Q2 on the right. (In
this view, the positive power bus is on the top of the board.)
- Components go on the top of the board. Component leads go through the
board.
- Mount the first transistor. On the bottom of the board,
bend an eight of an inch strip of each lead over. Typically, bend the base lead toward
the front of the circuit. Bend the emitter and collector leads toward the back of the
circuit.
- Mount resistors. On top of the board, adjust the resistor position. The longer component lead should be on
the transistor side of the component. Then you can later probe the transistor lead when
you're troubleshooting the circuit. You can also clip in additional components, such as
frequency-altering capacitors. On the bottom of the board, bend resistor leads over the
appropriate transistor lead and bus line. The resistor lead should cross these other parts
at about a 90-degree angle.
- Keep leads straight. On all devices, avoid hooking the leads. Keep leads as straight as possible. When you need
to bend a lead, try to keep the bend straight.
- Cables. Keep cable runs direct.
- Solder connections on the bottom of the board. Start with resistors. Tack-solder
resistor leads to the power or ground bus and the appropriate transistor electrode.
- Clip excess lead lengths. Where possible, leave a little extra
lead length so that the part is reusable.
- Mount and solder the other parts in the first transistor circuit. Then with the
second transistor circuit, follow these same practices.
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