Ed Worst edworst at att.net
Wed Aug 17 14:37:05 EDT 2005

I've noticed for some time that some of the switches on my TenTec gear seem
to be, well, mushy.  The Mode Switch and the Band Switch are especially
prone to this.

It turns out it's the knob, not the switch, and the problem is that if you
overtighten the setscrew, the inner circle of the knob cracks and doesn't
maintain a firm grip on the shaft.  Take one of those knobs off and look at
the underside and you'll see what I mean.  There's a circular gap between
the inner circle which fits the shaft and the outer circle which is where
the body of the knob begins.  (Seems like a poor design, given the function
of the knob.)

I thought that if I filled in that gap in the knob, it would make the knob
solid and less likely to crack when the setscrew is tightened.  So I tried
some J-B WELD as filler, and it worked.  First, I had to restore the inner
ring to its original position.  This was done with a flat wooden toothpick,
but other items will work also.  Just don't plan on re-using this spacer
because it'll become a permanent part of the repair.  Mix about a 1 inch
stripe of Part A and Part B of the J-B WELD together, and carefully fill in
the gap.  The J-B WELD has the consistency of toothpaste, so you'll have to
work it down into the gap.  I used another flat toothpick to do this.  Wipe
off any stray epoxy before it sets.  The package recommends a 15 hr cure
time, and I'd recommend following this recommendation.  The last thing you
want is to apply any stress to the epoxy before it's fully cured.  By the
way, I chose J.B. Weld because it seems to be readily available at any
autoparts store, and also because the description on the package states, in
part, "The city of Dallas, Texas repaired a cracked Caterpillar engine block
with J-B WELD and saved $4,000.00 plus 30 days down time."  If it's good
enough for that, it should be good enough for plastic knobs.

So, if you have this "mushy knob" problem, give J-B WELD a try.  It works
for me.

ed - k9ew

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