Stripping enamel from toroid wires

[John Wiener]

Ron,

I found a similar technique that improves the ease of stripping.  I  
start the blob of solder on the very end of the wire, so it heats the  
copper directly, then I drag the blob toward the toroid...seems to  
work for me.

When soldering the toroid in, I also heat the pad a little longer  
than usual to assure a clean joint.  Can't do this too long, though  
or you'll pop the pad.

I am awaiting a part (diode) from Elecraft (they've been great).  
This is the only thing between me and Alignment Part II.  I'm DYING  
to actually receive on 40M.  Then I'll relax and realize that this  
thing, in my hands, will actually work!

John
AB8WH
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Ron D'Eau Claire-2]

John AB8WH wrote:
When soldering the toroid in, I also heat the pad a little longer  
than usual to assure a clean joint.  Can't do this too long, though  
or you'll pop the pad.

-------------------------

Your technique of starting at the cut end is a good one. I've seen it
recommended elsewhere too.

I know some long-term builders who very successfully heat their toroid wires
far more than I would while soldering them in place. They get away with it
because they've developed a technique through long practice. As we gain
experience we develop our own methods, and that's FB.

When writing the assembly instructions we try to be conservative so the
builder will be successful the first time, even if he/she has never done
that procedure before.

I think the real serious mistake most builders make that leads to the
dreaded poorly-tinned toroid lead (PTTL) problems doesn't have much to do
with how well they tin the leads as *where* they tin the leads. That is,
they tin the leads up near the body of the toroid but not close enough so
that when they pull the leads through the pads, they pull all the
nicely-tinned lead through and end up with a section of enameled wire in the
solder pad hole!

Normally, it's FB to tin the wire all the way up to the core. I even unwrap
a quarter turn to make sure the well-tinned wire goes to where it touches
the core. The cores are not conductors, and it doesn't hurt if the tinned
wire touches it. One only has to be careful of transformers in which the
windings could be shorted if the tinned wires touch each other.

Another important point is to *not* pull the wires too tight through the
pads. I just pull 'em snug and bend them over on the opposite side and
solder, like any other component lead. Tugging with the pliers while
soldering makes it easy to sometimes pull enough wire off of the core that
the enameled wire gets pulled into the pad again, and some builders have
been frustrated to have the wire break away from the toroid core when they
pulled just a bit too hard. And then there's the "cold solder" joint that
results if the wire being held tightly in the pliers is released a moment
too soon after heating the pad so it moves slightly while the solder is
still plastic. It may seem very solidly soldered in the hole, but it is a
poor joint that will come back to haunt the builder later with a
high-resistance or intermittent connection developing as oxidation builds up
around the wire. It'll behave much the same as a connection that was never
soldered, but it's a lot harder to spot than an unsoldered lead.  

As usual, I find that extreme measures normally create more problems than
solutions, whether we're trying to build a rig, fix a leaky faucet or get
along with our neighbors <G>

I recommend checking after soldering each toroid lead to be sure solder
clearly flowed up onto the wire "above" the solder pad on the toroid side.
If the enameled wire seem to "dive" right into a now-hard puddle of solder
in the pad, that's a clear sign that part of the wire is not making contact
the pad. If they're lucky the bottom end did, but Gary regularly discovers
new rigs sent to him for 'repair' that have the wire well-trapped in the
solder in the pad but which never make contact with the pad through the
sheath of enamel that extends all the way to where it was clipped on the
bottom of the board. If it's inspected with a strong magnifier, it's
sometimes possible to see a tiny black ring around the wire where it exits
the solder. That's the enamel keeping the wire from making contact with the
pad. That's not a fool-proof check, though, since it's sometimes very hard
to see the ring.    

Having spoken for tinning the wire all the way to the toroid core, I should
point out that it is *not always* the thing to do, but when it is not, it's
described in the assembly procedure step. For example, in the KXB3080
installation, there's a small daughter board with two toroids on it and the
solder pads are very close together. One wire runs very, very close to
another wire's solder pad as it loops around the edge of the daughter board
to its own solder pad behind it. We tell the builder to leave 1/8" of enamel
on that wire just to avoid the possibility of a short circuit in case it
gets pushed against the solder pad.

There are been a number of builders who didn't read the procedure and tinned
the wire all the way to the core. Then they had to troubleshoot the KXB3080
assembly to locate the short. It's an easy fix: just pull the wire away from
the pad, but it underscores the importance of reading the procedures. Even
highly-experienced builders need to read each step and note the critical
information even if their method of doing the job is a little different from
what is described.

I tell builders to imagine they are defusing a bomb instead of building
their rig. Feel free to skip over any steps that they're willing to bet
their lives on <G>.

Some years ago I wrote a procedure for defusing explosives for the US Army.
They were ordinance fired from helicopters in Viet Nam. One day I was called
to Fort Ord where a sergeant, several field officers and I stood out on the
tarmac while the sergeant carefully followed my procedure to make the bomb
safe for removal from the helicopter. When he was finished and pronounced it
good, I was quite pleased and commented, "That's great! The guys in 'nam
shouldn't have any trouble with the real thing!"

One of the officers looked at me and, pointing to the ordnance on the
aircraft, said, "Oh that IS the 'real thing'. It's live! The sergeant knows
that ordnance well enough to have avoided setting it off if your procedure
had been wrong.... I think..."

It was a long time before I remembered to close my mouth.

Ron AC7AC

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[David Powell-10]

Ron D'Eau Claire wrote:

> For example, in the KXB3080
> installation, there's a small daughter board with two toroids on it and the
> solder pads are very close together. One wire runs very, very close to
> another wire's solder pad as it loops around the edge of the daughter board
> to its own solder pad behind it. We tell the builder to leave 1/8" of enamel
> on that wire just to avoid the possibility of a short circuit in case it
> gets pushed against the solder pad.
>
> There are been a number of builders who didn't read the procedure and tinned
> the wire all the way to the core. Then they had to troubleshoot the KXB3080
> assembly to locate the short. It's an easy fix: just pull the wire away from
> the pad, but it underscores the importance of reading the procedures. Even
> highly-experienced builders need to read each step and note the critical
> information even if their method of doing the job is a little different from
> what is described.

Thanks for a well timed comment, Ron.

I was just putting my KXB3080 together - and things weren't working -
when I read it. Over enthusiastic enamel stripping turned out to be the
problem here; in my case I've solved it in a rather inelegant fashion by
putting two (very) short lengths of insulation from some hook up wire
onto the end of L2-1 and L1-1.

It would have been much better to get it right first time, of course,
but it all works now - I've just had my first 80m QSO on the KX1.

So - thanks again.

David - G3XLW
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com