[Elecraft] N0SS' Nice comments on toroids

[redmen1969 at optonline.net]

Nice job Tom, a very thorough explanation.

I would ask for clarification on one item.  I asked this to the list a while back and received an answer relative to Elecraft but not to toroids in general, so I'll ask your opinion, here.

Your comment about not stripping enough enamel off of the leads is well taken.  This can easily result in inserting insulated wire into the PC board and not getting a proper connection.

My question is this.  Is there a danger of stripping too much of the enamel off?  In other words, if the bare wire makes contact with the core will this cause a short?  Taking it one step further, if both leads are stripped and come in contact with the core would this cause more problems?

I was told that the cores which Elecraft uses are insulated so this is not a concern.  Is this true?  Is this also generally true of other cores.

And lastly, how close to the core should the stripping be?

Thanks
Tom, WB2QDG
K2 1103

----- Original Message -----
From: Tom Hammond <n0ss at earthlink.net>
Date: Thursday, May 20, 2004 3:00 pm
Subject: Re: [Elecraft] Trouble With Toroids

> Hi treat:
> 
> >Can someone enlighten me as to the proverbial problem that seems 
> to come 
> >up with torriods? Just build a K1 and found the torroids 
> straightforward 
> >to wind, strip and tin. The unit fired up flawlessly. Maybe it's 
> because 
> >I'm a sailor and found winding torroids an awful lot like 
> whipping line 
> >(wrapping small twine around the end of rope so it doesn't 
> unravel). 
> >Beginner's luck on my part? Or am I missing something?
> 
> Truthfully, and as you've already discovered, there's NOTHING 
> difficult 
> about winding toroids, but many first-time 'winders' approach the 
> thought 
> of winding their own cores with quite a bit of trepidation...
> 
>  1) They worry about whether the turns HAVE to be perfectly spaced.
> 
>     The simple answer is "No they don't", but if you're gonna be
>     showing off your finished 'baby' to others, you will want the
>     quality of your workmanship to be evident in cleanly-wound
>     inductors, where the turns are relatively evenly spaced and
>     (following the instructions in the manual) spaced to occupy
>     80%-90% of the entire available core, AND that they're wound
>     in the proper 'sense', with regard to the direction of the
>     winding of the turns.
> 
>     Toroidal inductors which have the requisite number of turns,
>     but on which the turns aren't well-spaced, may exhibit a
>     slightly different inductance, but generally NOT to the point
>     that it will make a significant difference in the performance
>     of the radio.
> 
>  2) They worry about accurately counting the number of turns.
> 
>     This IS an important point. You MUST apply the required number
>     of turns to the core... no more, no less (unless required to
>     do so as a result of other value variations within the circuit),
>     and this usually involves only one (1) single turn added or
>     removed.
> 
>     Each time the wire goes THRU the center hole of the core,
>     counts as ONE TURN. Even if you just stuck the wire thru the
>     core and soldered it on each end to the PC board, that's still
>     ONE TURN. When I wind toroidal inductors, I usually kinda
>     'muck up' the first turn laid on, so I'll usually wind a couple
>     extra turns, count the total turns applied, and remove and
>     extra turns from the 'front' of the coil, so any boogered up
>     turns are removed. I ALWAYS count turns once I've completed
>     applying them to the core.
> 
>  3) They worry about being able to adequately strip and tin the
>     inductor leads.
> 
>     This is also a VERY IMPORTANT point. Fully 75%-80% (maybe more)
>     of the Elecraft service problems sent to Gary Surrency (AB7MY),
>     Elecraft's Chief Tech, result from PTTLs (Poorly Tinned Toroid
>     Leads). Some builders seem to get in too much of a hurry to
>     tin the inductor leads and, as a result, wind up not doing a
>     suitable job of removing the enamel and thus not getting a
>     well-tinned lead.
> 
>     There are numerous methods of stripping and tinning toroid
>     leads, and I'm not about the start another (almost religious)
>     thread on the 'best' method to use. Suffice it to say that,
>     properly done, ANY of the recommended methods WILL produce
>     nicely tinned inductor leads, suitable for your Elecraft kit.
>     However, it only takes one single PTTL to mess things up to the
>     point that a LOT of troubleshooting may be required to fix a
>     problem which should never have occurred in the first place.
> 
>     Another important point is to ensure that you tin the lead
>     all the way up to the core, so that when the lead is pulled
>     tightly within the PC board hole (ready for soldering) you
>     have not managed to pull un-stripped wire down into the hole
>     where it will not produce a good solder joint.
> 
>     Like they say, "There's never enough time to do it right, but
>     always more than enough time to do it over".
> 
>  4) They worry about how to mount the toroidal inductors so they'll
>     be solidly affixed to the PC board and not 'flop' around.
> 
>     Fortunately, with the K2, this is not a terribly significant
>     problem as there are only a couple toroidal inductors which are
>     in sensitive frequency-determining circuits and these inductors
>     are pretty easy to mount securely.
> 
>     The toroidal inductors which are mounted vertically, and there
>     are a number of them, DO NOT have to be affixed TO the PC board
>     with glue or other fixatives. If they are installed properly,
>     by their leads, they will be securely installed and will require
>     no further attention. When I install toroidal inductors
>     vertically, I stick their leads thru the PC board, bend the
>     leads slightly, to hold the core in place, and solder each lead.
>     THEN, I go back, grasp each lead with a pair of needle-nosed
>     pliers, exert a light pull on the lead WHILE reheating the
>     soldered junction. This allows me to remove the last bit of
>     slack which might have crept in while I was doing the initial
>     soldering of the leads.
> 
>  5) They worry about wearing out their fingers while winding.
> 
>     Can't argue there. Winding toroids, especially of you work to
>     ensure that each turn has been laid on tightly and smoothly,
>     can tend to make your fingers a bit sore.
> 
>     I've found that if I 'form' the wire around the outside edges
>     of the inductor core before I lay on the next turn, when I do
>     lay the turn on, it will readily conform to the pre-set bends
>     and it will not require nearly as much pulling and yanking on
>     the wire. Resulting in less finger fatigue.
> 
> That's about it! Winding toroidal inductors CAN be difficult IF 
> you make it 
> so. But then again, it doesn't have to be. It does take some care 
> in 
> winding, but then this is a radio you WANT to take care with, so 
> you'll be 
> proud of the end result... so it's worth the effort.
> 
> 73 and happy winding.
> 
> Tom Hammond    N0SS
> 
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