Elecraft K2 Owner's Manual User Manual

Page 59

LECRAFT

Transformer T6 is mounted vertically, near the middle of the

board. It uses a different winding technique where the wires for the
two windings are twisted together before winding ("bi-filar"). Cut two
12" (30 cm) lengths of enamel wire, one red and one green. Twist
them together over their entire length. The wires should cross over
each other about once every 1/2" or 12 mm.

Wind the twisted wires onto a 3/8" (9.5 mm) ferrite core (FT37-

43), using exactly 10 turns. Use the same method you used when
winding non-twisted wires, covering about 85% of the core. Figure
6-19 shows how the winding should look from two views (your turns
count will be 10 rather than 8 as in the drawing).

(RED)

(GRN)

(RED)

(GRN)

(a)

(b)

Figure 6-19

Clip and untwist the ends of the red/green pairs so that the leads

of the transformer look like those in Figure 6-19 (b). The pin numbers
shown match the component outline, with the red wires numbered 1-3
and the green wires numbered 2-4.

Strip and tin all four wires. Be careful not to strip the leads so

close to the core that the red/green wire pairs might short together.

Install T6 vertically, with the wires inserted as indicated in Figure

6-19 (b). Pull the leads taut on the bottom, then solder.

Sort the slug-tuned shielded inductors into two groups: 1 µH

(small slot, red line, quantity 4) and 4.7 µH (large slot, no mark,
quantity 8).

Install 4.7 µH inductors at L30 and L34 (large slot, no mark).

Press these inductors down as far as they’ll go before soldering.

Install the components listed below, starting with C39 in the back

left corner (near the key jack).

__ C39, .001 (102)

__ C4, 820 (821)

__ C5, 100 (101)

__ C9, .001 (102)

__ C7, 100 (101)

__ C8, 820 (821)

__ C108, .01 (103)

__ W6 (option bypass jumper)

__ D1, 1N4007

__ R38, 1 k (BRN-BLK-RED)

__ D2, 1N4007

__ RFC1, 100 µH (BRN-BLK-BRN)

__ C107, .01 (103)

__ C109, .01 (103)

__ C110, .01 (103)

__ D3, 1N4007

__ D5, 1N4007

__ D4, 1N4007

__ R37, 100 k (BRN-BLK-YEL) __ R39, 1 k (BRN-BLK-RED)

__ C113, .01 (103)

__ C114, .01 (103)

__ W1 (option bypass jumper)