KPA 100 L16 and RFC1

[raycollins]

I am constructing the KPA 100 and have just fitted L16 and RFC1 (both blue cores wound with 37 turns of 26 gauge wire).  I am having difficulty getting the two toroids to sit securely on the PCB because the leads do not align with the holes in the PCB so preventing the toroids from being pulled tight against the board.  The toroids seem quite wobbly and I am concerned that with shock and vibration, the wires will break.  Any suggestions?  How about a very small amount of epoxy adhesive between toroids and PCB taking care to avoid the windings?

Many thanks,

Ray  
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[Jim Wiley]

Ray -

Is it possible that the toroids are wound the "wrong" direction? Check
the assembly illustrations carefully.  It makes a difference whether the
winding starts in a "clockwise" or "counter-clockwise" manner as to
whether or not the leads line up with the solder holes in the PC board.  
Use of adhesives to secure coils is usually not recommended - although I
cannot see how it could hurt, performance wise. Securing the toroids to
the board could make future servicing difficult.  There have been few or
no reports of toroids coming loose or having wires break, even in mobile
service.

- Jim, KL7CC


On 12/9/2012 1:31 PM, Ray Collins wrote:

> I am constructing the KPA 100 and have just fitted L16 and RFC1 (both blue cores wound with 37 turns of 26 gauge wire).  I am having difficulty getting the two toroids to sit securely on the PCB because the leads do not align with the holes in the PCB so preventing the toroids from being pulled tight against the board.  The toroids seem quite wobbly and I am concerned that with shock and vibration, the wires will break.  Any suggestions?  How about a very small amount of epoxy adhesive between toroids and PCB taking care to avoid the windings?
>
> Many thanks,
>
> Ray
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> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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[Don Wilhelm-4]

Ray,

I have  only once found a toroid with a broken wire, and I suspect the
builder nicked the wire when he was stripping the leads.

Yes, those 2 inductors have the holes in line with the silkscreen shape
of the inductor.  There is no good reason why the cores have to align
with the silkscreen, just snug up the leads and solder.

If you insist on using a fixative of some kind, a small dab of hot melt
glue on either side of the core should be more than adequate. I do not
recommend epoxy - if you ever have to re-wind the toroids, you will not
get the epoxy off either the board or the toroid core.

73,
Don W3FPR

On 12/9/2012 5:31 PM, Ray Collins wrote:
> I am constructing the KPA 100 and have just fitted L16 and RFC1 (both blue cores wound with 37 turns of 26 gauge wire).  I am having difficulty getting the two toroids to sit securely on the PCB because the leads do not align with the holes in the PCB so preventing the toroids from being pulled tight against the board.  The toroids seem quite wobbly and I am concerned that with shock and vibration, the wires will break.  Any suggestions?  How about a very small amount of epoxy adhesive between toroids and PCB taking care to avoid the windings?
>

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[K1FFX]

Hi, Ray ... the top picture in my construction blog posting on building the KPA 100
(you can find it at http://build-k2.blogspot.com/2011/01/kpa100-completed.html)
may be of some help.   You can see that neither L16 nor RFC1 line up with the
silk screen particularly well, but the leads lined up OK and I was able to secure
the two parts to the board ... neither of them ended up flopping around, and no
additional glue material was needed.

Cheers -

Bruce
K1FFX