[Elecraft] Staking Toroids on K2
Jack Smith
jack.smith at cliftonlaboratories.com
Sun Feb 25 16:45:55 EST 2007
Don:
The material I used is Dow-Corning 748, identified as a "non corrosive"
"food grade" product. If you find yourself in need of an
electronics-compatible sealant, I can recommend it. I ordered the D-C
748 from McMaster-Carr, and here's how they describe it:
*748 Noncorrosive— *Use where low odor is desirable. Bonds to metal,
plastic, glass, and rigid PVC. Resists moisture and weather and works
with corrosion-sensitive electrical and electronic equipment. Begins to
harden in 30 minutes. Temp. range is -67° to +350° F. Complies with FDA
regulation 21 CFR 177.2600 covering indirect food contact. UL listed.
A 3 ounce tube is $7.48, so you will pay quite a bit more than the
hardware store stuff, but it does exactly what you need in an electronic
sealant. There are other D-C electronic sealants with different
viscosity. The 748 is similar to standard RTV in viscosity and handling.
Jack K8ZOA
www.cliftonlaboratories.com
Don Wilhelm wrote:
> Jack,
>
> Thanks for the additional comments.
> The original post had specified the GE Silicone II adhesive that he
> had on hand. In my experience that is not a 'properly selected
> silicon compound'.
>
> The last tube I had of that I started to use on some terminals on an
> aluminum vertical - well I had a copper wire attached, and it turned a
> sickly green within two weeks. I had to scrape it all off (a tough
> job), use new hardware and wire. I vowed never to use any that was
> not specifically marked as 'electronic grade'.
>
> 73,
> Don W3FPR
>
> -----Original Message-----
>
> 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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>>
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