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Joined: Dec 2002
Posts: 1,250
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djk Offline OP
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For anyone who hasn't wired a UK plug. This flash game I stumbled across gives you a fair idea how to do it.

Get it wrong and you'll blow up the TV
http://www.presencemultimedia.co.uk/bitsnbobs/wiringaplug/index.html

Joined: Sep 2002
Posts: 909
N
Member
Would'nt the TV blowing up be a good thing?

P.S. Did try the game,and the TV, sadly did not blow up.

Joined: Jul 2002
Posts: 8,407
Member
Dave,
I was able to blow the TV up by transposing the Phase and Earth wires. [Linked Image]
Anyhow,
Thanks for posting this, it would make a really neat learning tool. [Linked Image]

Joined: Aug 2001
Posts: 7,520
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Hey, good fun but it's a little technically inaccurate.

I managed to blow the fuse by transposing line and neutral.

Better yet, I blew up the TV by making the correct connections but leaving out the fuse! [Linked Image] [Linked Image]

Joined: Dec 2002
Posts: 1,250
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djk Offline OP
Member
yeah they're a bit off on the technicalities [Linked Image]

Should work fine with the neutral and phase transposed.. and how many TVs have an earth!?
...

The only thing you could really go wrong with is wiring the earth to the phase [Linked Image]

[This message has been edited by djk (edited 02-27-2005).]

Joined: Sep 2002
Posts: 1,498
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C-H Offline
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I just have to play the devils advocate here:

In a real world situation, you have two wires from the telly. Is there any way you can wire them so that an immediate danger arises in a properly wired house?

Joined: Aug 2002
Posts: 1,691
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DJK

The reason for connecting the live and neutral sides properly is that some TV sets, if you reverse the polarity of the flex, you are making the metal "chassis" live.

I don't know if this is an issue with modern TV sets but some old sets used to have metal cabinets, so....there probably could have been a danger of shock.

[This message has been edited by SvenNYC (edited 02-28-2005).]

Joined: Dec 2002
Posts: 1,250
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djk Offline OP
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Sven,

I doubt that has ever been the case in Western Europe as the plugs are 100% reversable and non polarised.

All appliences have to be able to operate safely in either polarity over here.

perhaps old british sets might be an exception to this due to the polarised plugs.

Joined: Jul 2002
Posts: 8,407
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Sven,
Quote
The reason for connecting the live and neutral sides properly is that some TV sets, if you reverse the polarity of the flex, you are making the metal "chassis" live.
Most TV sets these days, by virtue of the PSU have a "Hot-Chassis" running at half mains supply voltage, during thier normal operation.
Someone could also prove me wrong on this one too!.
C-H,
Quote
In a real world situation, you have two wires from the telly. Is there any way you can wire them so that an immediate danger arises in a properly wired house?
Well, with only 2 wires there are only 2 ways that the TV plug can be wired (if you discount the Earth terminal).
One is the right way and the other will not really cause a hazard as such, but it will mean that the internal fuse in the TV set will then be in the Neutral.
If the TV is the Double Insulated type that uses a standard Wire-wound Transformer, the polarity of the plug wiring isn't going to make an ounce of difference really. [Linked Image]

Joined: Aug 2001
Posts: 7,520
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The old "live chassis" TV sets in Britain had one side of the supply connected directly to the chassis, but the design was always such that nothing was exposed to touch. Fixing screws holding the chassis in place went into insulating inserts, the control knobs were non-conductive and either a push-fit on the control shafts or fixed with recessed grub-screws which could not be touched, etc.

Many of these sets in the 1950s/60s were fed from a reversible 2-pin 5A plug, so the chassis could easily be hot. The only problem was if somebody messed with the physical arrangements (e.g. replaced a fixing screw with one too long) or if a knob became detached and left a live shaft exposed (I learned that lesson the hard way when I was about 9 years old!).

The half-wave rectifier arrangement on the sets meant that in those areas which still had DC supplies in the 1950s the chassis would have to be live in those houses fed from the negative pole of the 3-wire distribution system.

The SMPS arrangements of modern TVs do indeed result in the chassis sitting at about half supply potential, no matter which way the power is connected (just one of the reasons for using an isolation xfmr for servicing).

Quote
In a real world situation, you have two wires from the telly. Is there any way you can wire them so that an immediate danger arises in a properly wired house?
Certainly nothing that would blow up the TV!

Reversed line and neutral = No problem.
Connected between neutral & ground = TV just doesn't work.

Connected between line & ground = RCD/ELCB trips if present, otherwise TV works using the ground conductor as a path back to the neutral.

There's no immediate danger in the latter situation, although a bad ground connection could result in the metalwork of other appliances being pulled up to 240V by the path through the TV.

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