[Elecraft] K2 L33

[Tom Hammond]

Scott:

>I have a question about L33 in the BFO circuit on the K2 I am building. The
>wire it is wound with appears to have a coating of some kind on it. Should
>this coating be removed before soldering it to the resistor that holds it
>in place? And if so, how can it be removed without destroying it. I tried
>scraping the coating off but that didn't work. The wire broke. Instead of
>taking off a couple of turns and using it anyway, I ordered a new one. I
>sent an email to support at Elecraft about this, but they don't answer
>emails anymore.

1) Losing a couple turns off L33 is NOT a show stopper!!!

2) L33 SHOULD have had each of its leads pre-tinned, copper-colored out to
    within 1/2" or so of the end and then solder covered to the ends. Thus
    all you should have had to do was to wrap the tinned ends around the
    resistor lead and solder into place.

3) The enamel covering the copper wires is 'heat-strippable'... but it takes
    a goodly amount of heat, and a bit of time to accomplish the task, BUT it
    is MUCH better (though possibly not easier) and attempting to strip the
    enamel using a sharp blade (which can, and will often will, cut the wire).

    IF you must strip heat-strippable enamel from a wire, get your iron nice
    and hot (750 deg F or higher), melt a small blob of solder onto the tip,
    STICK the END(!) of the wire INTO the solder blob and let it 'cook' for
    several seconds. Soon, you should see smoke and the enamel starting to
    melt and bubble up. At this point, add just a bit more solder and slowly
    insert more of the wire into the blob, until the required length of wire
    has been heat-stripped. Then SLOWLY pull the wire back out the same way
    you inserted it. This should leave you with a nicely stripped and tinned
    lead. You may have to use your fingernail to scraps away any remaining
    burnt (black) enamel from the tinned wire.

73,

Tom Hammond   N0SS