[TowerTalk] TIC Potentiometer
k1ttt at arrl.net
Fri Apr 4 09:26:47 EDT 2014
I have 5 of them up in the air, some getting pretty old, and haven't
replaced a pot in at least 10 years, so far back I can't remember the last
one I did... in fact I just went and found the bag of spare parts for TIC
stuff... I bought 3 clarostat pots in 2003 and still have 2 of them.
David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Scott
Sent: Friday, April 04, 2014 13:18
To: Patrick Greenlee
Cc: towertalk at contesting.com
Subject: Re: [TowerTalk] TIC Potentiometer
Yea it's a shame a multi thousand dollar piece of equipment is rendered
useless by just a drop of water. Some people have never had a problem like
this. Some like us up here have helped keep vishay in business lol. Seems to
happen less in dry environments like out west etc.
I've spent thousands of hours thinking abt these problems. It's crazy.
Always a stupid little thing that causes them to fail.
Had thought abt putting silicone on the shaft also and may work, in my case
I never thought there would be enough heat inside the Bellhousing to dry
that washer out. Was happy to see we got a few seasons out of that mod. Have
seen pots go bad on brand new rotors less than 2 weeks old. Any of these
that has the shaft pointing up this is more susceptible to happen to. No
drain for water to get out...
> On Apr 4, 2014, at 8:59 AM, Patrick Greenlee <patrick_g at windstream.net>
> Scott, A very innovative and cost effective idea that fender washer. Do
you suppose maybe a little silicon rubber (RTV) carefully applied might
give the washer a longer life. I suppose you could just form a washer of
your own out of silicon rubber caulk and after it cured sufficiently make a
small hole for the shaft. Silicon rubber caulk like the good GE or Dow
Corning stuff seems to last forever and never seems to harden of get age
> Patrick NJ5G
>> On 4/4/2014 7:28 AM, Scott Bullock wrote:
>> John one thing I have done with some success with prosistel rotors is to
put a rubber fender washer with a 1/8" hole in the middle over the shaft of
the pot right at the shaft/bushing of the pot. The small diameter hole
causes the washer to "warp" down at the edges and makes it look like a
little Chinese tiki hat. It sheds any condensation/water coming down the
shaft. I got 3 years out of that until the rubber started to dry out and
become hard. We had zero problems until this happened. It was the most
trouble free time we've ever had with these. Could be very easily done on
the ring rotors too fwiw.
>>> On Apr 4, 2014, at 8:18 AM, john at kk9a.com wrote:
>>> Apparently there are at least two common TIC ring problems, gear
>>> slippage and indicator failure.
>>> Gear slippage should not occur if the guide roller holds the ring
>>> gear against the motor. The further the motor is from the roller the
>>> more likely it will disengage. I have not seen this problem with my
>>> older style units.
>>> The sensor is a potentiometer and unfortunately it is mounted in a
>>> box that is not very waterproof. A pot with an IP67 water resistance
>>> rating would sure be nice but I have yet to find one. Most pots
>>> that I have found seem to have no shaft seal and with them facing
>>> upward eventual failure is likely. Switching to a different
>>> positioning indicator such as a reed switch is also a possibility, but
this is a major design change.
>>> John KK9A
>>> To: "towertalk at contesting.com" <towertalk at contesting.com>
>>> Subject: Re: [TowerTalk] TIC Potentiometer
>>> From: "Zivney, Terry" <00tlzivney at bsu.edu>
>>> Date: Fri, 4 Apr 2014 02:17:42 +0000
<towertalk at contesting.com">mailto:towertalk at contesting.com>
>>> I seem to recall K1TTT said the earliest rings used a pulse counter
>>> instead of the pot. The implication being that the pulse counter
>>> approach had problems and was upgraded to the pot.
>>> A basic problem with putting the whirling magnet on the motor shaft
>>> is that it
>>> only counts how many times the motor shaft turns. But, many of he
>>> appear to skip or slip or miss a beat (whatever you want to call
>>> it). So, the ring location is computed by counting the number of
>>> rotations of the motor, not the rotations of the ring.
>>> In my case, the pot reliably follows the motor and the spur gear
>>> that is supposed to drive the ring. The problem with inaccurate
>>> readout is not caused in these cases by the pot but rather by the
>>> spur gear and ring gear losing contact from time to time.
>>> It seems that is also the case with the ring in the recently posted
>>> YouTube video of a TIC ring problem.
>>> A pulse counting technique that is counts motor revolutions is not
>>> inherently superior to a precision potentiometer geared to that same
>>> motor. The selected pot is a ten-turn pot which has lots of
>>> resolution potential (sic).
>>> Terry N4TZ
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>>> TowerTalk at contesting.com
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