[Boatanchors] Johnson KW Matchbox - Problem with the "matching capacitor

[Richard Knoppow]

    I have one of the smaller Matchboxes but I think perhaps the 
capacitors are of similar design. I looked at it. The both caps 
have a sort of spring clamp on shaft The clamp has a nut on it 
which is adjustable. The centering seems to be done with another 
nut on the shaft on the outside of the frame. This one is on the 
inside between the frame and the rotor. I have trouble describing 
it. There are two on the split cap and one on the tuning cap. I 
think these may adjust the drag on the shaft. At any rate one can 
adjust them with a small open end wrench of a small slip pliers. 
Worth looking at since you have yours open. I was going to open 
the thing anyway because I am planning to use it to feed a 
balanced antenna. I don't know for certain this is a drag 
adjustment. You can tell if it affects the centering. The rotor 
should be precisely centered in the stator.
    I also found out that the very elegant Johnson knobs have 
only one set screw. Not so good, they really should have two.
    I am also not sure how the scales are supposed to be aligned. 
I set the tuning cap at 100 for full mesh and the split matching 
cap at 50 for half way. Seems to make sense. Let me know if this 
proves helpful.

On 10/29/2020 1:10 PM, David Propper wrote:
> Hi all,
>
> I am refurbishing a KW Matchbox that someone had previously converted to a “coax “ only (ie: unbalanced” tuner).  The “Matching” variable capacitor will not stay in a “set” position once adjusted and the “rotors” constantly want to hang down at the bottom of the variable capacitor.  I don’t see a spring to use to adjust the tension on the shaft so that it stays in place once adjusted for proper tuning. Can someone explain to me how to tighten the tension on the capacitor shaft ?
>
> I am also looking for a pair of the ceramic standoff insulators mounted on the rear of the KW Matchbox for the “balanced feedline” to attach to.  Does anyone have a spare set available ?  If so, please advise.
>
> You can reach me at k2dp at charter.net <mailto:k2dp at charter.net>
>
> Thanks and 73,
> Dave, K2DP
> St. Louis, MO
>   
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL