[Elecraft] K1 Construction. Preparing Toroid Wires and soldering techniques.

[Don Brown]

Hi

It seems like you are making it too hard. The tinning process you are doing
is almost what is required to do the heat striping. The problem with
scraping and/or sanding is the risk of nicking the wire. Here a few tricks
for heat striping.

After winding the toroid cut the leads to about 3/4 inch. The enamel acts as
a heat insulator so it is hard to get the striping started up next the the
toroid so start at the clipped end of the wire. Place your iron on the end
of the wire and apply a good amount of solder forming a blob. The heat will
start to flow up the wire and the enamel will begin to bubble up just in
front of the blob. As the enamel burns off keep moving closer to the toroid
and keep adding more solder. You must add more solder to keep a good amount
of flux in the blob. If the blob is not bright and is not smoking you need
more solder. The flux is what helps clean the lead.  Keep a piece of
cardboard under the toroid so the excess solder that drips from the blob
will not burn your bench. Stop when the blob is just touching the core. You
should have a clean stripped and tinned lead right up to the core.

When installing the toroid insert the wires into the holes. Pull the wires
tight from the back side with needle nose pliers and bend the wires sideways
against the board to hold the toroid tight while you solder. The joint
should be bright with a good filet around the lead.

You can also use a heated solder sucker type iron (like a Hakko 808) to
strip the wires. Just insert the lead into the nozzle, add some solder, wait
a sew seconds and pull the trigger.

Hope this helps

Don Brown
KD5NDB

11 K2's and counting (#12 in work now)
3 K1's
5 KPA100
2 KAT100
all options many times


----- Original Message -----
From: <Martin.Evans@simoncarves.com>
To: <elecraft@mailman.qth.net>
Sent: Friday, April 04, 2003 4:21 AM
Subject: [Elecraft] K1 Construction. Preparing Toroid Wires and soldering
techniques.


> Greetings guys. I've just completed construction of the KFL1-4 filter
board
> for my K1 and just thought I would share a few thoughts on toroid leads. I
> know the elecraft approved method is heat stripping, but I didn't have
much
> joy with this method myself, so I fell back on my normal tedious method of
> scraping the enamel off. I used the edge of a small (1" dia) model makers
> abrasive wheel but any other abrasive tool would do. It's a bit fiddley
and
> you need to keep rotating the wire to make sure you have all the enamel
> off, (wire must not be damaged ie knicked) but it does the trick. When
> tinning I used a nice hot iron and applied small amounts of solder 2 or 3
> times. I find that if you try to tin the whole lead with one application
of
> solder, the flux burns away too fast and it only "takes" on part of the
> lead and you end up with a blob of useless old solder hanging off it.
> Better to use a very small ammount of solder and tin a small part (say
> 1/4") at a time  and using fresh solder each time. When tinned, you can
use
> light abrasion to gently scrape off any tiny black dots of burnt flux. I
> also applied IPA is a degreasant before tinning (but maybe didn't need
to).
> Anyhow I found that this works for me, the leads all soldered straight
away
> to the PCB.
>
> I think lots of beginners don't realise that once fresh solder has melted
> it must be run and in place within 3 secs prefferably less, any longer and
> you need fresh solder. The flux only does it's job for a few seconds if
> that. eg if the solder doesn't take/run immediately it is applied, then
> remove iron, clean wires/pad of old flux and repeat with clean tip and new
> solder, don't fiddle about with it, quit and start again. Hope this helps.
> Soldering is a bit of an art and we all do it differently, you've just got
> to find what works for you.