Elecraft KAF2 User Manual

Page 3

Firmware Requirements

To use the KAF2's real-time clock, you'll need main microcontroller firmware revision 2.01 or later. If you
have an earlier version (1.xx), you should have received an upgrade. You can install the firmware upgrade
during assembly of the KAF2 (as explained later), or you can install it ahead of time.

Note:

The main micro is U6 on the K2 Control board. To check your firmware revision, hold any switch

when powering up the K2. When you release the switch, the revision will be shown on the LCD (left side).

Assembly

A fine-point, temperature-controlled soldering iron (700-800 degrees F maximum) is

required to assemble the PC boards. A higher-wattage iron or one with a wide tip may damage
components, pads, or traces. We also recommended the use of a Panavise (or equivalent bench vise)
and an illuminated magnifying glass to facilitate PCB and connector assembly.

To avoid soldering conflicts, install components only in the order described below. Double-

check all values before soldering, since removing parts from double-sided PC boards can be difficult.

Locate the KAF2 PC board and identify the top and bottom sides. The side of the board with outlines

of the ICs (U1-U4) and most other components is the top; the side with the "KAF2" label is the bottom. If
an assembly step does not specify top or bottom, the component should be installed on the top side.

On the top side of the board, install the two 1N5711 diodes, D1 and D2. The cathode end of each

diode has a black band which must be aligned with the banded end of its PC board component outline. The
leads of the diodes must be bent very close to the body in order to fit between the two pads.

Make sure D1 and D2 are seated flat against the PC board, then solder and trim the leads.

The leads on small capacitors can be fragile. When handling capacitors in the following

steps, do not pull on the leads or bend them excessively.

There are two different types of .01-µF capacitors supplied. Both are labeled ".01" or "103", but they

have different lead spacing. Locate the two .01-µF capacitors with 0.1" (2.5 mm) lead spacing, as well as
the four with 0.2" (5 mm) lead spacing. Separate them into two groups.

Note:

For all remaining assembly steps, you should solder and trim component leads after installing each

group of components unless otherwise instructed. Leads can be trimmed before or after soldering, but trim
them as short as possible.

On the top side of the PC board, install the four .01-µF capacitors with 0.2" (5 mm) lead spacing:

__C3, __C4, __C7 and __C8.