Glad you found the problem John, one of the good things about the Tri-ex
LM-470 I have is that you can unplug the limit switches and switch in to
by-bass mode, this would have made it much easier to find you problem with
your US Towers-472P.
I had a problem here for the longest time with my Motor tripping the circuit
breaker as soon as the key power switch was turned on, it turned out to be a
dry solder joint on the over temperature switch located in the junction box
on top of the motor housing. It took me all winter to find it, luckily
there are good guys on this reflector like Skip KJ6Y who faxed me the wiring
diagram for the control box wiring.
Mike, K6BR
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of John Farber
I had a stuck US towers motorized 472MDP, 72 foot motorized tower, with
the remote control RM-1000 unit. The symptoms were on the remote control
box in the shack, the lights for up and fully up were on as well as both
lights for fully down and down were on and the tower would not move up
or down, either from the shack or from using the remote switch at the
base of the tower.We were in the middle of our stormy season here on the
West Coast,
and I wasn't comfortable leaving the tower fully extended with a high
gusty winds we were experiencing. Over a couple of phone calls to US
towers I was told to remove power to the control box on the base of the
tower fabricatees and jumpers
install a jumpers power up the tower and lower it. Unfortunately I
didn't really get a break in the weather for weeks, and felt
uncomfortable working on a tower when there was this high probability of
lightning. So I left the tower fully extended, and took a different
route. I've posted my problem to the tower reflector, and got several
suggestions but one of them really hit home. Someone suggested that the
limit switches were notorious for getting water in them. So the first
clear day I investigated and found sure enough there were signs of water
in my lower limit switch. I copied the numbers off the limit switch, an
Alan-Bradley 802T, AP, series H. unit. I then set about trying to locate
one. I found they had a retail value of something like $175 ouch! So I
tried eBay, for the first time and wound up buying one new switch and
one used switch just to have a backup. It turns out that the switches
have a clam shell design. Upon opening the switch there is a smaller
black plastic unit which is actually a microswitch with spade connectors
on it. These Alan Bradley switches are described as plug type. The
actual part that had failed was the small black plastic microswitch unit
inside the much larger two-part outer shell. Today I tackled the fix for
this unit, and wound up splitting apart the clam shell on the old
switch, and swapping out the black plastic microswitch inside. This
approach saved me from having to deal with unhooking the wires into the
clam shell and dealing with the other waterproof cable clamp on the
bottom of the clam shell. The change out took me perhaps 10 minutes, and
the most difficult part was getting a reluctant screw out without
stripping it. Upon checking the tower function after doing the
replacement all is well. So in conclusion, I didn't have to make up any
jumpers or mess around with the relay box at the base of the tower and I
didn't even have to change out the whole limit switch-only that small
black plastic microswitch inside the outer housing. By the way I was
able to find a replacement limit switch for $30 on eBay. I hope this
information helps anyone in the same situation. 73, John Farber, KG6I
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