[TowerTalk] US Tower HDX-589MDPL UP/DOWN switch failure

[Joe Subich, W4TV]

 > While the use of a 4PDT switch to include the switching of the hot
 > lead would not be a bad idea safety wise, it still would not solve
 > the issue if the neutral contacts shorted during actual operation,
 > as in my case. The overall switch would still be in the on position
 > while moving the tower.

The overall tower would remain in operation while the switch was in
either the up or down position.  However, placing it in OFF would
stop the motion.  Yes, a limit switch failure would still result in
no limit in the direction of the failure but you could certainly make
sure you had positive manual control by switching both neutral and
hot.   This would avoid the need to "pull the plug" or trip the GFCI.

If you wanted extra safety, there is no reason the limit switches could
not be replaced by double pole switches with the two poles connected in
series.  That way if one pole fails shorted the other may still do its
job.

73,

    ... Joe, W4TV


On 2015-07-02 11:21 AM, K2CB wrote:
> Joe,
>
> Good point on the two switches wired in series being an issue once
> the tower reaches one of the limit points. In over thinking things,
> that fact slipped my mind.
>
> While the use of a 4PDT switch to include the switching of the hot
> lead would not be a bad idea safety wise, it still would not solve
> the issue if the neutral contacts shorted during actual operation, as
> in my case. The overall switch would still be in the on position
> while moving the tower.
>
> At least the motor would not buzz when the switch is returned to the
> off position if one set of contacts failed. But then again, that
> could be a bad thing, because then you would not know if there it was
> a failure with one of the other pole's contact set.
>
> I guess the best solution is just to do periodic testing, and hope it
> does not fail in the wrong circumstance!
>
> Eric K2CB
>
>
>
>
>>
>>> Looking over the wiring diagram for the control box after the
>>> fact, I am questioning why UST did not just simply wire the two
>>> limit switches in series, then just use the UP/DOWN toggle switch
>>> to break the connection between the series-wired limit switches
>>> and the motor.
>>
>> With the limit switches in series you would not be able to move
>> the tower off either limit.
>>
>> It would be better to use a 4PDT center off to switch hot/neutral
>> or a using separate switches - one to control direction the other
>> to switch power.  The problem with the two switch version is the
>> need to remember to stop motion before reversing direction.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>>> On 2015-07-02 12:34 AM, k2cb at comcast.net wrote: I recently had an
>>> interesting issue with my HDX-589MDPL tower.  I am posting my
>>> experience, hoping it saves someone from a potentially
>>> catastrophic event. ********
>