Elecraft KSB2 - Manual (Page 12)

12
i
Very small ferrite cores are used for RFC1 and RFC2 to minimize stray signal coupling. These
cores are a little harder to work with than larger cores, and are also more fragile. If you find it necessary to
hold them with a vice, use only plastic or rubber jaws and a minimum of pressure.
Inductor RFC1 is wound with 19 turns of red enamel wire (9" [23 cm]) on an FT23-43 core. Since
this winding completely fills the core, you may end up with one or two turns overlapping each other on the
ends, which is acceptable. The edges of the core are sharp, so while winding, try to avoid scraping the wire
against the core. Prepare the leads as you did with T1 and T2, but leave them long (about 1").
Install RFC1 on the top of the board, even though the component outline appears on the bottom (in
the crystal filter area). The component outline identifies the proper holes to use. Insert the leads into these
holes from the top, then pull the toroid down until it is seated on the board between RP1 and X3. Before
soldering, look at the leads with a magnifying glass (if necessary) to make sure that all insulation is
removed where the leads intersect the pads. Solder RFC1 on the bottom and clip the excess lead length.
Wind and install RFC2 in the same manner as RFC1.
Use an ohmmeter to verify continuity (< 1 ohm) between the pads for RFC1. Do the same for RFC2.
In the middle of the board, directly above the "C23" label, you'll find two pads connected by a white
line. Install a 1/4" (6 mm) tall U-shaped ground jumper between these two pads, on the top side of the
board. The jumper can be formed from a discarded component lead. (One of the thick leads from a 1N4007
diode is ideal.) This jumper can be used as a ground point for test instruments.
Re-check the orientation of the following using the Parts Placement drawing:
__ ICs __ Resistor Networks __ Diodes
__ Transistors __ Electrolytic capacitors
Carefully examine both sides of the board for solder bridges and cold solder joints.
i
Before handling microcontroller U1, touch an unpainted, grounded surface. U1 is a CMOS IC that
can be damaged by static discharge.
Install U1 in its socket. The notched or dimpled end of U1 should be nearest the left edge of the
board. (Pin 1 is indicated by a round pad on the board.)