Severing PCB lands, was [Elecraft] Keying Mod; Construction technique

[Tom Hammond]

Hi Paul:

At 11:31 PM 11/14/2005, you wrote:
>I just purchased the KPA100 for my K2 (serial
>3640), and in going over the instructions I see
>that the installation of the keying modification
>is highly recommended.  I'm a little nervous
>about the part of the mod that requires the
>cutting of a circuit trace.  What's the best way
>to perform this operation?  (Kind of a shame to
>have to hack at my K2 this way, but you gotta do
>what you gotta do.)

It's not THAT difficult to do, though it does take some 'intestinal 
fortitude' to do it if you've never done something like that before. <G>

The way I do it is to use an Xacto knife with a new (e.g. sharp) blade.

Note - If you use the 'standard' Xacto knife & blade, the tip of the blade 
will probably break as soon as you press down hard on it!!!  But that's 
actually OK< since you really want to be able to use the next-in section of 
the blade anyway, 'cause it's stronger... heheh!

First, DO NOT (ever) DRAW the blade across the land being cut!!! This 
almost always guarantees you'll slip somewhere along in the process and 
drag the cutting surface across several other lands (not intended to be cut 
or TOUCHED by the blade).

Place the blade, about as flat on the land as you can, and press it 
directly DOWN onto the PC board. This will take some effort, and as I noted 
above, will often cause the thin tip of the blade to break off. Just 
re-group and re-start with the thicker end of the tip now available.

Once you have made your initial downward cut, move the blade about 0.05" 
(less than 1/16") to one side of the first cut and repeat the effort.

Once you have made two cuts in the land, use the sharp edge of the blade to 
get under and lift the cut section of land free of the PC board. A little 
added (angular) pressure to get under the cut section of the land will help 
here.

Some folks have also had success using their soldering iron tip to heat 
just the severed section of land, cause it's adhesive to loosen, and then 
lift the copper free. I've used this method as well, but find the above 
method to be a bit safer in some respects since it doesn't run the chance 
of accidently overheating and lifting the ends of the cut trace as well.

If you're going to attach a component across the severed land, once you 
have the land severed and the cut-out section removed, use your Xacto knife 
(or whatever knife you're using) with the blade FLAT against the ends of 
the severed land, to scrape off a bit of the green solder mask. Repeat 
until the copper is bright and shiny. Then quickly (and lightly) tin the 
bright copper, using moderate heat and minimal solder.

This is only the way _I_ do it. Before you jump in, be sure to read other's 
responses as well and then use the one you feel most comfortable with.

73,

Tom Hammond   N0SS