[Elecraft] Staking Toroids on K2
Jack Smith
jack.smith at cliftonlaboratories.com
Sun Feb 25 15:35:25 EST 2007
Don:
I agree with you that nothing is required to secure the toroids to the
K2's PCB, it is not the case that a properly selected silicon compound
causes damage.
"Neutral cure" or "electronic grade" silicon will not cause damage, as
it sets up without emitting the acetic acid given off with the typical
RTV found in hardware stores. I ran tests last fall to determine the
effect of RTV upon Q and inductance of 4uH toroids, wound on T50-2 cores
for the Z10010 4.915 MHz bandpass filter I provide along with the Z90/91
panadapters, where the purchaser plans to use it with a K2. To the best
of my ability to read the HP4342A Q-meter, there were no changes in Q or
inductance after the neutral cure silicon rubber cured. The particular
product I used was a Dow-Corning compound, which gave off a faint smell
reminiscent of peppermint. About half the filters I built use it to
secure the toroids to the PCB. I abandoned it half-way into the
production run as (a) the wire leads, it turned out, were adequate and
(b) it was extremely difficult to apply without getting it all over the
PCB. I wound up doing post-assembly work with an Xacto knife, trimming
pieces of cured RTV from locations they did not belong.
I also ran tests to determine the effect of Q-dope on the same inductors
and found that the effects were somewhere between negligible and the
limit of my ability to measure. (For the newer hams, Q-dope is used to
secure windings to a coil form and is basically polystyrene dissolved in
toluene.) I decided to Q-dope the majority of the inductors I wound for
about 35 filters (140 total toroids) as method of assisting the long
term stability of the Z10010 filter, which is a bit touchy if the flat
nose and symmetrical flanks are to be maintained. A few filters were
assembled without Q-dope as a comparison, and they seem to work just as
well.
Still, as I said at the start of this message, I agree 100% with Don't
recommendations--don't use either RTV or Q-dope in your K2 assembly.
Jack K8ZOA
www.cliftonlaboratories.com
Don Wilhelm wrote:
> Mike,
>
> Use NOTHING to secure the toroids other than their leads. In the 7+ years
> of the life of the K2, I have never heard of a failure die to a fractured
> toroid lead, and there is one that I know of (I built it) that served for a
> couple years as a mobile rig in the cab of an 18 wheeler - I am certain that
> one saw more than normal shock and vibration.
>
> Any securing compounds can cause damage - be particularly careful of the
> silicone glues. The GE Silicone II that I have found smells like vinegar
> and will cause a green corrosion mess when in contact with copper (could
> even destroy the K2)
>
> Elecraft recommends no fixatives for the toroids, and the use of them may
> void the warranty, so go forth with it at your own peril.
>
> 73,
> Don W3FPR
>
>
>> -----Original Message-----
>>
>> All,
>> My K2, serial no. 05625 is complete and has been on the air for three
>> weeks today, but I'm still in the process of adding accessories. I've
>> mostly run it on 80 and 40 m with excellent results.
>>
>> One question I have for the group- Has anyone found a need for
>> protecting the vertically mounted toroid inductors from mechanical shock
>> events during portable operations? If so, what staking material is
>> recommended? I am concerned about degrading exposed conductors with
>> anything I might use for an adhesive. I think the GE Silicone II
>> adhesive I have on hand is used for preventing corona or ionization
>> around high voltage terminals so maybe it would be a good candidate?
>>
>> 73
>> Mike Mussler
>> AI8Z
>> K2 serial 05625
>>
>>
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