I don't have the same tower, but similar. And had a similar situation once.
My tower uses Square-D industrial limit switches. While these are well-made
all-weather devices, their internal gaskets may eventually dry out or leak
water, which will result in corrosion inside the switch. By the time my
system was shorting, both the upper and lower limit switches were severely
corroded inside. These switches are easily replaced, and in many cases you
can replace/repair internal parts. Once repaired/replaced I recommend
putting a bead of silicone caulk around all the seams, and also the fitting
where the cable enters the switch.
The other thing to look out for is the outer insulation on the cables to
the limit switches, even though rated for outdoors/sun/oil/heat, will
eventually crack and fray, exposing the internal wires which will then not
last long. If you are going to repair the limit switches, it is good to
consider replacing the wiring from the control box to the limit switches.
Good luck and 73
Dan
K0DAN
-----Original Message-----
From: Larry Loen
Sent: February 17, 2013 08:41 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Latest Tower Woe -- Short I can't fathom
I'm struggling with my remote control (aka "remote head") on my tower. I
have yet to raise it and it's now a real issue.
Here's the thing: I had carefully (or so I thought) wired from the tower
to the shack. When I applied power to the remote unit, I got a short severe
enough to blow the fuse. I originally thought the fuse somehow came that
way (maybe in transit?) so I blew a second fuse proving the problem was
real.
Anyone have enough knowledge of these things to comment? Maybe I'm missing
something obvious here...
Here's the deal.
1. The US Towers remote head has a user-installed control cable. The
cable has positions C1, C2, C3, C4, C6, C7, and C8 (yes, there is no C5).
All else is pre-wired.
2. I wired at the tower, at my "grounding station" at the tower, at the
grounding station next to the shack entrance and at the remote head
itself. I checked especially the 110 feet of buried wire before doing
anything. That wire doesn't short within the buried run for sure.
3. After the failure, I noted that two wires seem permanently shorted.
Since the manual is a masterpiece of understatement, and hard to follow,
I'm not sure that this is right or whether the tower would function
temporarily without one of the wires.
4. I did prove that the problem, if it is a problem, is in the tower
wiring. I simply removed one of the "shorted" wires at the tower and the
short disappeared. I also traced the two and one of them appeared to be
the "tower is down" limit switch, which appears to be engaged. Since the
limit switch is a spring loaded affair, I put in a small bit of scrap wood
for a moment "just to see" if it would eliminate the short, but the short
persisted.
5. The AC wiring does not have any obvious problems at the remote.
6. There is no AC power being applied at the tower side during all of this.
Larry Wo0Z
Some added detail:
Here's what I learned about the wiring by doing a long series of continuity
checks on the unit at the in-shack remote:
Switch box findings
Zero Ohm ...
C1 connects C6 when "RAISING" switch
C2 connects C6 when "LOWERING" switch
C3 connects C6 when "LOCAL" switch
C7 connects C6 when "LOWERING" switch
C6 appears to be the "power" source.
C2 and C7 are shorted together. However, they do not connect through C6.
Experiment shows they are shorted together on the tower side (disconnect my
C2 at the tower proves this).
C1 and C4 100 ohms raise/lower off
C1 and C4 15 ohms raise
C1 and C2 100 ohms lower, remote
C1 and C2 Inf local
C1 and C6 100 ohms when lower, 0 when raising
C1 and C7 100 ohms when lower, no connect when raising (remote also)
C1 and C8 100 ohms when lower, no connect when raising (remote also)
C2 and C4 15 ohms lower and remote
C3 and C4 15 ohms local, no connect otherwise
C4 amd C7 15 ohms lower and remote are no connect otherwise
C10 and C11 15 ohms when power switch on C12 no connect
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