[TowerTalk] HF2-V Doorknob Capacitor Failures

Bill Jackson Bill Jackson" <k9rz@radiks.net
Fri, 22 Sep 2000 23:05:53 -0000


I have a Butternut HF2-V 80/40m vertical that has served me well for over 10
years.  The only problem I have experienced is the periodic failure of the 200
pF, 10 kV, door knob capacitor on the 80m coil assembly.  I have had to replace
this cap about every 3 years or so.  The failure mode is usually rather
spectacular, occurring with a loud bang and pieces of the capacitor ending up
several feet from the antenna. It appears that maybe moisture is getting into
the capacitor causing a flash over which ends up destroying the cap.

I have thought about using some type of sealer on the ends of the cap to prevent
the moisture from getting in.  I am hesitant about this as I don't want to
affect the electrical characteristics of the cap.  Has anyone done this before
with any success and if so, what type of sealer did you use?  Someone suggested
using RTV, but having learned from towertalk about the acidic properties of RTV
type sealant, this doesn't sound like a very good idea.

Any thoughts?

Thanks in advance.

Bill - K9RZ

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