component and pushing them through the holes,
aka through-hole vias (Figure
D
). Resistors do not
have polarity: place them either way round.
Angle the legs by splaying them slightly
outward so that the components are held in
place. Solder each leg by heating both leg and
pad (the shiny ring around the via) and feeding it
solder to create a joint. An ideal joint will be shiny
and smooth with a slightly concave surface. (If
your joint appears dull or has too much or too
little solder, don’t worry — you can rework it, just
be careful not to heat the components or board
excessively with your attempts.)
Now snip the legs off with diagonal cutters to
keep things tidy and prevent short circuits.
2. LED
Unlike the resistors, LEDs do have polarity. The
longer leg indicates the anode, or positive leg.
LEDs also typically have a “flat” side, indicating
the cathode, or negative leg. If you’re not certain,
use the diode setting of a multimeter to check.
Push the legs through the holes for the LED,
marked on the PCB with two concentric circles.
Be sure that the long leg is through the + hole and
the flat side is opposite it. Solder and snip.
3. TRANSISTOR
The transistor (Figure
E
) is what creates the
oscillation in our circuit, and the oscillation is
what creates the sound! Remove the middle
(base) pin from the transistor with the diagonal
cutters (Figure
F
), cutting it as short as possible.
Push the remaining outer legs through the holes
marked 2N3904 on the PCB, with the flat side
toward the bottom. Bend, solder, and snip!
4. CAPACITOR
While some capacitors do not have polarity, this
2.2µF electrolytic capacitor does, as indicated
by the large minus (–) symbols aligned with the
negative leg on the component’s case. Find the
2.2µF label on the PCB, ensure the – leg goes
through the hole opposite the +, make sure it’s
fairly flush to the PCB, then bend, solder, snip!
Your board should look like Figure
G
.
5. AUDIO JACK
In order to get sound out of our circuit, it’s
connected to a 3.5mm mono jack. Orient the
three pins as indicated on the silkscreen, then
solder and trim (Figure
H
).
6. POTENTIOMETER
The trimmer potentiometer (or “knob”!) lets you
change the pitch, or frequency, of the sound by
varying the resistance. Because of the force that
you’ll exert twisting this small pot, it has two
heavier legs (Figure
I
) in addition to its three
active pins. These may take a little more solder,
but be sure to fill the larger through-hole via and
create nice joints so your potentiometer is secure.
DIY USIC: Oscillator Synth Module
50 makezine.com
Joe Bauer, Nick Gaydos
C
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D
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M85_048-51_SS_AvalancheOsc_F1.indd 50M85_048-51_SS_AvalancheOsc_F1.indd 50 4/10/23 3:33 PM4/10/23 3:33 PM
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