Alive TV Splitter

[nev25]

I installed a 4 way Tv signal splitter under the house a few months ago.
The signal is split 4 ways 3 go to the individual bedrooms and on the the lounge.
The splitter is a passive (no power) all metal casing (Obviously for shield)
To cut a long story short I was under the house today and touched the device and got a boot .
I went and got my trusty multi meter and measured between the device and a copper gas pipe (assuming the gas pipe was a good earth)
To my surprise It measured around 112Vac.
As I said the device is passive and no power injection anywhere I cannot see how this is possible apart from a faulty TV??

Any Ideas?

[Uncle Bob]

Hi Nev, I've had zaps before (more than one occasion) from just touching the antenna. I suspect the oscillator may back feed in some sets.

Might pay to ask this question in the electronics forum over at austech.info

[scooter]

Hi Nev, I've had zaps before (more than one occasion) from just touching the antenna. I suspect the oscillator may back feed in some sets.

Had the same zaps, often on the ear as you brush it while mucking about under it doing up the clamp or similar. Assumed it was some sort of voltage coming back from the TV set.

[journeyman Mick]

A mate of mine installed aerials etc for a living for a number of years and told me a while back of this danger. It appears that high voltages can be present at the aerial socket on the television. On multiple connections like Nev's this voltage can build up (or multiply or whatever, not sure of the terms) to produce high voltages. Apparently on apartment buildings where there are a large number of sets all connected to one aerial array this can and has been lethal. Or so he told me, according to industry publications that he'd recieved. Sounds plausible to me, but then I'm no electrician or electronics type person.

Mick

[Ausyuppy]

Nev,
That is perfectly normal to have aroun 110v AC sitting on the chassis of your electronic equipment. Due to the way switchmode power supplies work and no earth reference, you will find the voltage floating on the chassis.

The only time I was concerned was when I received a stronger "tingle" off a satellite decoder box I used to have. Its voltage on the chassis was 240v AC. Upon close inspection, turned out that the power lead was terminated onto the power supply the wrong way around, active --> neutral, neutral --> active. This surprised me as normally these things dont care, however I guess in the design of this power supply it did, hence the power lead being plugged into the power supply directly, as opposed to the figure 8 lead that is normally used on the back of the boxes.

It doesnt hurt to earth the splitter if possible, as you may notice there will be an earth point on the splitter. Quite often people wont have this issue anymore as plasma / LCD TV's are earthed. Therefor all equipment connected in your home theatre systems (including antennas) will be earthed via the leads to the plasma earth. For a while, Foxtel was installing a wall plate that had a earth lead connected to a plug which was to be plugged into a GPO. This earthed the satellite cable, which in turned earthed everything else.

Journeyman Mick,
You will feel the tingle easier if your well earthed, ie on your roof, or for me, playing with my satellite dish in the backyard barefoot. Then you become the path to earth. Easiest way to get rid of this issue is to earth your equipment. If there is multiple equipment connected and there is a box that is faulty like my old satellite decoder box, there is always a potential to get electrocuted.

Cheers
Steve