[Elecraft] securing toroids in K2, why not?

[Ron VE8RT]

Thanks Don,

     I've received a few helpful responses already, which I  
appreciate.  I could do without the RTV, except I like it at RFC14  
because its jammed into a tight space, and as you mentioned, its a RF  
choke which wouldn't be critical.

     For a very long time conformal coating has been used in my  
field, avionics.  Its great stuff to reduce board corrosion in damp  
environments, even if its just from condensation.  That is if its  
applied carefully and the board and adjustable components and  
contacts are well masked.  If it won't mess things up, when its  
finished I'd like to apply conformal to parts of the board,  
especially the underside of the board.

     Back to the RTV on RFC14, there is a very small dab of it on the  
bottom of the core, just to keep it upright.  Anymore than a small  
dab would be a waste.

     OK, future cores I'll leave alone unless the manual says  
otherwise.  And conformal coating parts of the board can wait until I  
look into this further.  I have spare cores and wire, and an  
reasonably good LCR meter at work, I'll see what difference the  
coating makes in the value of toroidal coil.

               Ron

On 2-Jul-11, at 7:29 PM, Don Wilhelm wrote:

>  Ron,
>
> I suggest that you indeed do that.  Actually on RFC14 it will  
> likely make little difference because the exact inductance is not  
> critical, but once the RTV hardens, you will have a bear of a time  
> getting it off should it ever need replacement.  Do not use any  
> fixatives on any more of the K2 toroids.  Many compounds will alter  
> the inductance, and it is just not necessary.  To emphasize that  
> point, I often refer to the K2 that I built for an OTR truck  
> driver.  That K2 lived for years in the cab of his 18 wheeler, and  
> never suffered any toroid damage - the toroids were adequately  
> supported by their leads.
>
> More specifics, T5 (and sometimes, but not often, the inductors in  
> the LPF) may need "tweaking" by adjusting the turns spacing.  The  
> use of any fixatives will prevent that, and require you to purchase  
> new cores and rewind the toroids.
>
> Build the K2 as specified in the manual, and you will have no  
> problems - if you add or subtract anything, it may not work correctly.
>
> 73,
> Don W3FPR
>
> On 7/2/2011 9:02 PM, R Thompson wrote:
>>     I just installed the first toroid, RFC14, in my K2 kit.  After
>> winding it, I sprayed it with conformal coating, and just before
>> installing it I put a small dab of RTV3145 (non-corrosive)  
>> silicone seal
>> on the end next to the PC board and then soldered it in place.
>>
>>     So.... I turn the page in the manual and the very next thing  
>> in bold
>> is "Do not use adhesives or fixatives of any king to secure  
>> toroids to
>> the PC board.
>>
>>     Would this also apply to conformal coating?  Should I remove  
>> RFC14
>> and take the RTV off it?
>>
>>

Ron VE8RT ve8rt at xplornet.com
Yellowknife, NT, Canada
62 26.765N  114 22.503W  Grid Square DP22tk
"Who are these that fly as a cloud, and as doves to their window?"   
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