Elecraft K2 Owner's Manual User Manual

Page 54

LECRAFT

Solder the pins on the bottom of the RF board. Solder a pin at

opposite corners first, then make sure the headers are resting against
the board. If necessary re-heat the pins while pressing the assembly
against the board. When the assembly is in position, solder all 8 pins.

Install U8 (78L05), which has a plastic TO-92 package like a

transistor. U8 is located near the front left corner of the board.

Option-bypass jumpers W5, W2 and W3 are located on the right

side of the board, near the crystal filter. Use component leads to make
these jumpers, or remove the insulation from appropriate lengths of
green hookup wire. These jumpers should be formed so that they lie
flat on the board, and should not touch any adjacent components.

Test points TP1, TP2, and TP3 are round, yellow, single-pin

female connectors. TP1 and TP3 can be found in the synthesizer area
of the board. TP2 is near the SSB option connector, J11. Install and
solder all three test points.

NOTE: There are five 100 µH RF chokes in the kit. If one is slightly
smaller than the others, set it aside to use at RFC15.

Install RF choke RFC13 (100 µH, BRN-BLK-BRN), near the

middle of the board. Orient the first color band to the left

Install the receive mixer, Z6 (TUF-1 or TOP-1), below the

"ELECRAFT" label at the middle of the board. Make sure that Z6 is
lined up with its component outline and is flush with the board before
soldering.

Install the electrolytic capacitors in the order listed below, starting

with C60 near the far left-hand edge. Insert the (+) lead of each
capacitor into the hole with the (+) symbol.

__ C60, 100 µF

__ C93, 10 µF

__ C103, 220 µF

Looking at the bottom of the RF board, locate U4 (MC145170,

near C90). As shown by the "X" in Figure 6-14b, the short trace from
pin 16 of U4 to C89 (on the top side) has been cut at the factory.

C90

MC145170

(bottom view)

Pin 16

Figure 6-14b

C90

C91

RFC15

Pin 13

C88

001

100

Figure 6-14c