John, you must be running that new prototype Alphapower amp! hi!
I have to retract my earlier statement about the Bourns pot being in the
Digikey catalog, as I couldnt find it there. Maybe it was the Mouser catalog?
(Now if I could only find mine!)
Anyway, thanks for the specific number, John.
73, Ty K3MM
-----Original Message-----
From: John Brosnahan <broz@csn.net>
To: w2up@itw.com <w2up@itw.com>; towertalk@contesting.com
<towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Saturday, May 23, 1998 13:02
Subject: [TowerTalk] TIC Ringrotor indicator problem
>At 12:29 AM 5/23/98 +0000, Barry Kutner wrote:
>>The indicator on my TIC Ringrotor is starting to act up again -
>>needle starts jumping around and rotor stops turning. I believe I
>>read somewhere that TIC was working on a fix, like a different kind
>>of indicator pot. Anyone know if they ever came up with something
>>that keeps on TICking?
>>Tnx/.Barry
>
>
>Barry,
>
>I had an original Clarostat pot fail in my TIC RIng and replaced it
>with a similar pot only to have it fail quickly thereafter.
>
>Subsequently I examined both pots and the failures seemed to be
>at the point of contact of the wiper arm, or in the wiper arm lead.
>I ultimately replaced the pot with a Bourns 3590S-4-501, which is
>what TIC Ring is supplying now. This pot is not listed in the
>usual distribution sources (they only go down to 1K, not 500 ohms)
>but it can be special ordered through the usual distribution channels.
>
>My gut feelign was that there was a chance that the failure mode
>was that of picking up RF on the control leads with the RF itself
>actually burning up the pot at the point of contact of the wiper arm or
>on the fine lead to the wiper arm. Failures would then be associated
>with lead dress to some extent and not consistent, which might
>explain why some have had failures and others have not. Since the
>control leads are almost in the middle of any antenna mounted on
>the ring the level of RF could be quite high. If the leads are pulled
>open into a loop that is terminated by the pot resistance the
>amount of dissipated power could be significant! I once had
>an extension cord that was tied in a knot to a small drill actually
>melt while in the field of a 10 KW FM transmitter. I have to stop working
>those antennas when they are hot! In fact my metal frame glasses
>got very hot to the touch, as well!
>
>So, I decided to add bypass capacitors on the terminal strip in the
>motor enclosure when I changed to the Bourns pot. I have not had
>any more failures but can't be sure if it was just due to the Bourns
>pot or to the bypassing of the pot leads.
>
>The whole arrangement of mounting and engaging the teeth on
>the pot gear leaves a lot to be desired, so there is still some suspicion
>that it is more a mechanical or environmental issue rather than an RF
>one, but so far so good.
>
>Hope this info helps.
>
>73 John W0UN
>
>
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