Elecraft XV Assembly Manual for XV222 - Manual (Page 38)

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The following transistor is particularly sensitive to
electrostatic discharge (ESD) damage. If you are not wearing a
grounded antistatic wrist strap, touch an unpainted, grounded object
before handling Q5.
Install transistor Q5 (2N7000) in the space provided in the lower
right quadrant at the edge of the PCB.
Install two 2-pin header connectors next to Q5.
__JP8 __JP7
Wind toroidal transformer T1 on the FT37-43 (gray) toroid core as
follows 3 . T1 uses a bi-filar winding, which means that two wires are
wound on the core together. The wires will be twisted together loosely
before they’re wound onto the core.
Twist the red and green enameled wires together over their entire
length. The wires should cross over each other 2 to 4 times per
inch (1 to 2 times per cm).
Wind 4 turns of the twisted pair on the FT37-43 toroid core as
shown in Figure 25 on the next page. Each time the wire passes
through the center of the core counts as one turn, so verify that
the wires pass through the toroid four times. Spread the turns
around the core as shown.
Separate the leads and trim them to a length of about
1” (2.5 cm).
3 A pre-wound toroid is available from an Elecraft-approved source. See page 2.
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In the next step the toroid leads will be stripped and tinned.
The leads must be prepared correctly to provide good electrical
contact when installed
.
Strip the insulation and tin the leads using one of the following
techniques:
1. Heat Stripping:
a. Place a small amount of solder (a.k.a. a “blob” of solder) on
your soldering iron.
b. Insert the clipped end of the wire into the hot solder. If the
iron is hot enough, you should see the insulation bubble and
vaporize after 4 to 6 seconds.
c. Add more solder and feed more wire into the solder as the
enamel melts. Continue tinning the wire up to the edge of the
core, and then slowly pull the wire out of the solder.
d. If any enamel remains on the lead, scrape it away using your
thumbnail or sharp tool.
2. Burning: The insulation can be burned off by heating it with a
butane lighter for a few seconds. Use sandpaper to remove the
residue, then tin the bare wires.
3. Scraping: Use a sharp tool to scrape the insulation away. Work
carefully and gently: do not nick the wire. Work around the
entire circumference of the wire to remove all of the enamel and
tin the bare wires.