[TowerTalk] Ham-IV problem

charlieo@tellabs.com charlieo@tellabs.com
Mon, 10 Nov 1997 12:59:30 -0600

I have a recently developed problem with my Ham-IV that I would like to share with the 
group in hopes of finding a solution.


Rotator was rebuilt/refurbished last May by a respected firm.  Up until last 
week, it had been performing flawlessly.

Rotator is mounted in 53' of 45G.  A Rohn TB-3 thrust bearing is used.  I have a 
21' mast with 17' above the tower.  At the 67' level is my homebrew 44' 
rotatable 40m linear loaded dipole, estimate 50 lbs. weight and 5 sq. ft. 
windload.  I built it to brick outhouse specifications.  At the 56' level is a 
TH6.  This combo has been working FB with rotator since Oct. 4th when thrust 
bearing (purchased new in Sept), mast, and 40m rotary were installed.  Prior to 
that, since last May, rotator was turning TH6 on 5' mast with "some other" 
non-thrust bearing used.

Again, up until last week, the system had been working fine without any 
problems.  During the time of failure, the system WAS NOT being subjected to 
high winds.

I had the array pointed at ZL (245 degs) and was moving north to JA (315 degs) 
when the indicator stopped at 285 degs.  I could not get the rotator to turn.  
Thinking that I had a bad motor starting cap, I left the system alone until this 
past weekend when I had some time to look at it.  Changed out the starting cap, 
but the system still would not move.  I moved the control box to the shack 
window, and could hear the brake solenoid CLANG when I depressed the brake 
lever.  By wiggling on the brake and the CW (right side) control, I got the 
rotator "unstuck" and moving.  I moved it to the south (via east) and stopped it 
and rotated it at various points.  All ok.  I then moved it back CCW, to the 
north, and stopped it and restarted it.  Again, all ok.  I then tried to take it 
to the southwest, but it stopped again, very suddenly, at 285 degs.

Thinking something was jammed up on the tower, I put on my climbing belt and 
went up.  I could not see any sign of anything binding or in any way 
interferring with the mast rotating.  Grabbing the mast and twisting it proved 
that the brake was holding fast, as I could only budge the mast a bit in either 
direction.  I inspected the rotator and rotator shelf, and all looked ok.  
Checked the bottom 4 bolts (that go through the shelf) for tightness, and all 
was fine.

Came back down the tower, and spent the next 30 minutes or so trying to get the 
rotator "unstuck" from 285 degs.  Finally got it to move again, CW, and repeated 
the steps earlier where I stopped and started it in various places to confirm 
that it was working.  It was.

So, I went back CCW with it again, and watching out the window to observe the 
turning (actual direction of ants and control box direction indicator do agree 
with each other...) and taking it to the west.... STOP again at 285 degs!!!

Back up the tower I went.  Thinking that something had settled, and perhaps some 
misalignment had occured as things settled mechanically, I loosened the rotator 
shelf from the tower legs, and tried to get the rotator to move again.  Still 
stuck.  Went back up the tower and retightened the rotator shelf.  The tower and 
the shelf are level.

I'm running out of time and antenna wx.  I've given up on SSB SS this weekend 
(no big deal, not much of a phone op) but do not want to be handicapped for CQWW 
CW at the end of the month.

I would greatly appreciate any input that you may have.


Charlie  N9CO  charlieo@tellabs.com

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