In message <9705051259.AA29478@hp-and2.an.hp.com>, Tony Brock-Fisher
>I rebuilt an XA last summer. It had only been up 2-3 years, so I was
>not expecting to have to replace the capacitor caps. But when I got it
>down, I found several were cracked.
>Here's an excerpt from a previous post containing relevant info:
>Initial visual inspection showed 7 out of 40 of the blue capacitor caps
>were cracked. I also did DC resistance measurements of the traps and
>found that most traps had a total series resistance of 30-50 mOhms
>(milliohms). Two of the traps had resistances of 200-300 mOhms. I traced
>the high resistance to the large end of the most outboard shorting
>strap (15 meter section).
>I called KLM and spoke to Bruce about the caps. He said they should have
>lasted 10 years in normal UV exposure, and that there were only 3 explanations
>for their premature failure. These were (1) installation with a hammer;
>(2) installation using oils as lubricant; or (3) bad lot of plastic.
>I told him I hadn't used (1) or (2), and he very kindly sent me a replacement
>set for NO CHARGE, to replace the set I had bought for the prior rebuild.
>I'd call that great service from an antenna maker!
>I rebuilt the antenna using the new caps. Bruce told me that the best way
>to install the caps was to warm them up in hot water. This is a great tip!
>They went on really easily once they were warm.
You have to be very very careful with the water idea. I did it and found
that unless you gave those end caps a good shaking and inspection they
introduced droplets of water into the assembly. The very opposite of
what they are intended to do. In the end I put them on with LIGHT taps
from a hammer - measuring all the while the distance between the caps.
This exercise was the result of a high SWR problem and I took the
antenna down and entirely rebuilt it. I noted that the distance between
end-caps was NOT as specified in the conversion kit - so it rather looks
like I did not do it right first time.... One learns.. By the way I have
pop-rivetted most of the connections now that the antenna plays fine.
Seems a better idea than sheet metal screws to me.
73 de Ron
>Hope this helps...
>-Tony, K1KP, firstname.lastname@example.org
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