LCD TVs

Honest John Back Room » General discussion ( non motoring )
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Tue 24 Sep 2013 22:42
LCD TVs - Doc

In the days of the cathode ray tube, it was said that a malfunctioning TV could catch fire while plugged in. Does this still apply to LCD sets?

I would imagine the danger is less as they use a far lower voltage.

Do you unplug at night?


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Wed 25 Sep 2013 10:05
LCD TVs - dan86

I dont think there's much danger of them catching fire. I dont unplug mine I just switch it off from the remote in the 7 years iv been doing it its never once caught fire.

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Wed 25 Sep 2013 22:20
LCD TVs - Bobbin Threadbare

Very unlikely - Sony did recall a lot of LCD tellies a few years ago but that was for a defective part that caused combustion!

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Thu 26 Sep 2013 18:03
LCD TVs - Colin_r

I've never unplugged my TV, and it has never caught fire ;)

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Fri 27 Sep 2013 00:01
LCD TVs - Leif

I've never heard of it happening. These days the biggest risk is from faulty Lithium Ion batteries and/or poor quality chargers. Also one brand of fridge is or was known for catching fire.

The old CRT TV had a large capacitor inside. Even if you turned it off, and took the cover off, you would risk a potentially fatal discharge.

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Fri 27 Sep 2013 00:49
LCD TVs - bathtub tom

I doubt you'll find anyone here who'll admit their TV caught fire, it's a motoring forum!!!!

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Fri 27 Sep 2013 21:43
LCD TVs - Leif

What a bizarre statement.

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Mon 30 Sep 2013 14:50
LCD TVs - concrete

Will the TV in my car catch fire??? Concrete

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Sun 13 Oct 2013 21:35
LCD TVs - Cyd

I would imagine the danger is less as they use a far lower voltage.

Really? The voltage of the mains coming in to your house is 230V nominal. Every device connected to your supply is designed to run on this voltage.

Actually, appliances of all sorts cause fires. Of particular concern to the industry at the moment are tumble driers, dishwashers and irons. Recessed downlights are also a severe fire risk if improperly fitted (which most are, because people won't pay to have it done properly and usually diy dangerously).

My last telly was a crt and went up in a blue flash about 6 years ago (I needed a reason to buy a plasma anyway).
Our last iron caught fire about a year ago when the wife left it on for about 30 mins unattended. Smoke alarms did their bit.
Our toaster went up in flames only a month ago.

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Mon 14 Oct 2013 11:10
LCD TVs - dan86

I dont think you should have electronic devices in your house you seem to be unlucky with them. Iv never had any of my electrical devices catch fire.

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Tue 15 Oct 2013 17:15
LCD TVs - Doc

I would imagine the danger is less as they use a far lower voltage.

"Really? The voltage of the mains coming in to your house is 230V nominal. Every device connected to your supply is designed to run on this voltage."

CRTs do run at high voltages using transformers. See article:

Above can be seen a typical power supply for a cathode ray tube. T1 is the mains transformer and V1 a high voltage rectifier such as the Cossor SU2150A. The transformer must produce 1kV to 5kV, depending upon the tube used.

www.r-type.org/articles/art-116.htm

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Tue 15 Oct 2013 20:07
LCD TVs - jamie745

Well I can see a riveting discussion has been taking place here.

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Wed 16 Oct 2013 17:26
LCD TVs - concrete

Well I can see a riveting discussion has been taking place here.

Oh no! not riveting again. Thought I gave that up when I left metalwork class.

Cheers Concrete

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Tue 12 Nov 2013 11:40
LCD TVs - buzbee

I get the impression you are living in some bygone age. The CV1120 valve base was designed before the last world war and is now a museum piece! The valve actually used was much smaller and, even that, quickly gave way to an even smaller semiconductor one.

The picture tube you refer to is for an oscillascope, rather than a TV. Whilst some early TVs used that (electrostatic) type of tube, TV quickly evolved to use magnetic deflection. IIRC that was in use in 1952 when I built a TV using an ex-government electrostaic radar tube so as to watch the coronation! -- money was tight in those days.

The later tube used a line flyback transformer in its horizontal scan circuit and the high voltage needed for the tube was derived from a winding on that. The voltage was more than 5KV. However, the energy received during a shock , if you toched it, although very upleasant, was not lethal if you were a healthy person. I accidently touched it a few times. Less than from a tazer.

I lost the text below during an edit! So I did it again, not knowing it had posted.

Take your pick.

Edited by buzbee on 12/11/2013 at 11:45

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Tue 12 Nov 2013 11:10
LCD TVs - buzbee

The cathode ray tube you show was for an oscillascope, not a TV, and the article is dated 1955.

Whilst some early TVs used that electrostatic type tube, it was superceded by ones that used electro-magetic deflection type, many years ago, and a line-flyback transformer was used in the side to side scanning and also magentic for vertical deflection.

The SU2150A valve base was designed before the last world war ! ! and is now a museum piece rather than a modern valve ! Much bigger than normally used. Indeed it became a semi-conductor one -- even smaller.

I get the impression you are living in some bygone age.

The anologue TV set, using a CRT, that has just gone obsolete, derived its' tube high voltage from a winding on the line timebase transformer. It will give you a very unpleasant shock, but is not usually lethal, unless you have a weak heart. I have caught my hand on it a few times. Also you would be looking at a much higher voltage, than 5KV.

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Tue 12 Nov 2013 23:38
LCD TVs - dimdip

^ interesting read, buzbee.

I think I may know the origin of this story.

Some years back, there was a spate of Sony TVs that had faulty on/off switches. (This is well before the recent Bravia fires – at least 10 years ago.)

Even though the TV was turned 'off'' at the on/off switch, the mains voltage broke across the insulation in the switch causing arc heating and eventually fire.

It's a very unusual type of fault, though for best Feng Shui, switch off at the wall at night.

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