K2 RF board - components on bottom?

[BobConvers]

 I was finally able to free up some blocks of time and begin construction of
K2 #4565.  This, and my construction of a KX1 earlier this year, is the most
satisfying and enjoyable experience in ham radio that I've had in years.  I've
also learned a great deal monitoring the discussions on the reflector.

My construction was proceding successfully (if slowly) up to the point in
Assembly, Part II, page 52, where components are connected to U4 (the PLL) on 
the bottom of the RF board.  I found this to be the trickiest part so far
(haven't begun the toroids yet!). 

After several failures, and much thought and preparation with pre-bending and
tinning of leads, I was finally able to get C91, C88, RFC15 soldered to the
correct points on the bottom of the board - with no shorts.  However, I now
have no continuity through RFC 15.  I assume that means I destroyed the choke
during the mounting process, so I'm ordering a replacement and will try again
next week.

Before I do that, does anyone have any words of wisdom on how to manipulate
and mount these components to increase my chances of success on the next
attempt.  Thanks.

Bob, WO3E
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[G3VVT]

 
 
In a message dated 26/03/05 15:27:54 GMT Standard Time, [hidden email]  
writes:

After  several failures, and much thought and preparation with pre-bending
and  
tinning of leads, I was finally able to get C91, C88, RFC15 soldered to  the
correct points on the bottom of the board - with no shorts.   However, I now
have no continuity through RFC 15.  I assume that  means I destroyed the
choke
during the mounting process, so I'm ordering a  replacement and will try
again
next week.



-----------------------------------------------
 
I found the easiest way to mount these was to get the component in  
approximately the correct position holding it with the end of a finger (asbestos  
tipped from many years of pulling hot tubes) and then quickly tack one end with  
solder to hold it. Then the component can be positioned correctly. First the  
opposite end is soldered and finally the end that was tacked soldered. RFC15 has
 to be handled with great care. I would recommend holding the RFC15 leads
next to  it's body with fine needle nosed pliers and then bending the free end of
 the lead to the required shape. That way strain is kept off the component.
Some  disagree with this method, but it does work successfully for me at least.
 
There are other components in the K2 that benefit from such gentle  treatment.
 
Bob, G3VVT

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[Don Wilhelm-3]

Bob,

This is the way I mount and solder RFC15:
Make nice gentle bends in the leads of RFC15 starting about 1/32 to 1/16
inch away from the choke body (close but not right at the body) - using
fingers only (tools may apply too much pressure without any tactle
indication) I bend the leads so they make a full 180 degree turn, ending up
with a half loop of lead at each end that has a diameter of about 1/8 inch
or slightly less.

Now I use the longnose pliers and hold the edge of the loop that is closest
to the choke body and bend the loose end of the wire down at about 45 degree
angle next to the plier jaws and then still holding the pliers in place,
grasp the very end of the lead and bend it upward - it should bend with a
smooth curve this time in contrast to the sharper bend at the edge of the
plier jaw.  This places a small offset in the lead. Do this at both ends of
the choke.  Now you should have the leads formed so that you can lay the
choke in place with both leads contacting the pads that they are to be
soldered to - if it doesn't fit, re-bend the leads again while protecting
the choke to lead junction with pliers as above.  Hold it GENTLY in place
and solder. Do not apply any stress to the leads, especially when they are
hot, and be certain the leads are formed to fit before doing any soldering.

It takes longer to tell than to do - form to fit and then solder.

73,
Don W3FPR

> -----Original Message-----
> ...
> After several failures, and much thought and preparation with
> pre-bending and
> tinning of leads, I was finally able to get C91, C88, RFC15
> soldered to the
> correct points on the bottom of the board - with no shorts. 
> However, I now
> have no continuity through RFC 15.  I assume that means I
> destroyed the choke
> during the mounting process, so I'm ordering a replacement and
> will try again
> next week.
>
> Before I do that, does anyone have any words of wisdom on how to
> manipulate
> and mount these components to increase my chances of success on the next
> attempt.  Thanks.
>
> Bob, WO3E
>

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[Ron D'Eau Claire-2]

Bob, G3VVT wrote:

I would recommend holding the RFC15 leads
next to  it's body with fine needle nosed pliers and then bending the free
end of
 the lead to the required shape. That way strain is kept off the component.
Some  disagree with this method, but it does work successfully for me at
least.
 
There are other components in the K2 that benefit from such gentle
treatment.
 
---------------------------

That's an excellent point.

I wince when I see someone grab lead with the needle-nose pliers next to the
part body and make a sharp bend by rotating the pliers. If those pliers
happen to touch the body while they're being rotated, they act like a lever
and can exert literally pounds of strain force pulling the lead out of the
part while only a few oz. of force is applied rotating them. Cracked part
bodies, pulled-out leads and broken connections are very common when leads
are bent that way.

I'm a great believer in "finger bending" leads. That is, I hold the part in
one hand and use a finger on my other hand to bend the lead, with no tools
at all. That almost always produces the correct radius for the part to drop
into the board with minimal force on the body. If the bend must be tighter,
I can usually do it by simply pressing on the bend toward the body of the
part to make it a little tighter. That way the force is toward the part, not
away from it.

Bob's approach is even more gentle, provided one doesn't move the pliers in
relation to the part and there's room for the width of the plier jaws before
the bend starts.  

Ron AC7AC


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