Thanks for that info. Our Ham4 pot failure so far has not been chronic.
The direction pot and rotor brake, in our case, had about 20 years of use
on it
prior to the failure. We have always noticed a slight rotational
oscillating sloppiness
in the wind, probably worse with wear on the brake teeth and brake armature
slot (?)
Norm's says that a little slop is supposed to be there, the brake does not
lock it up tight.
So some rubbing of the brush on the pot wire is going to happen regardless
as your boom wobbles slightly 24/7 in the wind.
Anyway, failed rotator pot is fixed now. We rolled up some copper sheet
into a rod
about quarter-inch in diameter and soldered it to the stub of the original
brush.
It has been working fine, and the resistance wire now has a lot more meat
to chew on
than did the original....
This installation is about 15 feet above the last guy set, and there is
noticeable
sway in the wind when one is at the top. Rohn 25 also makes a nice
torsion bar
to ease wind gust loads on the rotator. Some of the apparent
oscillation is likely due to twisting of the tower, that can be felt due to
antenna inertia
when up the tower and the second op down in the shack applies rotation for
test purposes.
Was a bit unsettling the first time that happened with a heavy 4-el quad in
1980......
Further Note: Unlike what we read in the Archives about Yaesu rotors, Ham
4's are quite user-friendly.
Parts are readily available stateside, and you don't have to be a Rocket
Mechanic to fix one.
The manual has instructions and there are a lot of relevant YouTubes....
Don N7EF
On Sat, Nov 8, 2014 at 6:46 AM, Steve London <n2icarrl@gmail.com> wrote:
> N7EF wrote:
>
> The one direction pot failure we ever had, at autopsy, revealed the
> rotator had been back and forth so many times
> that the brush riding on the resistance wire torus had completely worn
> away. What was left of it had sprung down
> so it was touching intermittently on inside diameter of the
> resistance wire torus...it was not a corrosion.issue.
>
> -----------------------------------------------------------
>
> I have never had this happen to one of my rotators, however I have seen it
> happen repeatedly to a local ham - and he was rarely turning his rotator.
> The issue was an incredible amount of wind-induced vibration on his
> TH7DXX-topped HDBX48 free-standing tower. Even on calm days, you could feel
> it. I finally convinced him to stretch a piece of black dacron rope between
> the top of his tower and a tree to dampen the vibration.
>
> 73,
> Steve, N2IC
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