Re: Antiference switches - bizarre fault



"Carpy" <carpy@xxxxxxxxxxxx> wrote in message
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"Bill Wright" <insertmybusinessname@xxxxxxx> wrote in message
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"jamie powell" <jamie_p84@xxxxxxxxxx> wrote in message
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"Bill Wright" <insertmybusinessname@xxxxxxx> wrote in message
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Do they shut off until mains power is cycled though?
Or do they get stuck in an endless power-on->overload->trip-off loop?

Most of them are clever enough to simply stay shut down until the
overload is removed. Presumably a few mA are allowed to flow through
the short circuited cable.

You *presume* they're not stuck in an endless loop??

I'd definitely want to check, especially if I was installing them in
places where line power wasn't needed and the circuit was permanently
shorted.

As an installer I have to have some faith in the basic competence of the
designers of the equipment that I install. Whether the devices are stuck
in an endless loop or whether they simply shut down and monitor a very
small current is immaterial to me, because the devices continue to work
regardless, which is all that concerns me. I gave up on worrying about
anything except things that have immediate impact on my existence a long
time ago.

That's the philosophical reply. The technical one is that since these
devices are used more often direct from an aerial than via a masthead
amp, it would be absurd for them to feed significant power into the
aerial input unconditionally. A device that was constantly and rapidly
switching a significant current (derived from the device's power supply),
on the RF input of the said device would very likely cause interference.

Bill


Well I've just had a call that the switch I mentioned above has now ceased
to function completely. Curiously I installed another one of these this
week on a different job, and the "Auto Line Power" light stayed lit when I
connected just a TCX10A. Surely this light should be off when there's
nothing being drawn by a masthead.
<snip>
There will be even more current drawn by the short-circuit aerial, what Bill
is saying is that the switch electronics is supposed to detect the
over-current
condition and either turn it off, or limit it to a safe value.
Because of the fault that existed in your unit, this over-current trip did
not work and my suspicion is that well over the stated 100mA was
being drawn by the aerial, maybe several amps, enough anyway to
make the 12V rail collapse. The isolator plug you fitted stopped this,
maybe you were very unlucky and some delayed damage was done.

--
Graham.

%Profound_observation%


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