Adding Headphone socket to TV

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Background: I have a portable TV which I want to add a headphone socket to.
Plan: Open TV. Find wires (probably just 2, I doubt it a 14", 80 TV has stereo) Add chassis mounted switch to the live (?) wire. Add chassis mounted headphone socket to the casing Wire the socket to the other 'side' of the switch
This will (I hope) leave me with a TV which I can switch between headphone and speaker modes.
thoughts anyone? M.
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Be VERY careful! Lethal voltages can be present inside a TV hours after it is turned off. Not a job for the novice.
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The headphone socket will incorporate a switch. There are 4 terminals on it.
You break the speaker cable at a convenient point and reconnect them, passing through the appropriate terminals (you may need to install additional cable if there is insufficient slack to position the socket where you want it. The terminals are -ve and +ve feed from the amplifier, and the switched -ve and +ve outputs to the speaker. The internal switch disconnects the speaker automatically when a plug is inserted.
Christian.
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Hi Michael,
Buy one of these : http://tinyurl.com/mcgf then drill a hole through the plastic casing to suit the size of socket, in an area that will not interfere with any of the innards. Find the speaker wires and trim them down or add to them until you have enough wire to reach the new socket. The black wire will be connected to the outer part of the socket (the socket casing) and the red wire will be connected through the two lugs on the end of the socket. When you insert the 3.5 mm Jack Plug, the action of pushing the plug in will separate the connection of the red wire from the main circuit board and the existing speaker and will make the connection to the headphone jack plug only.
This is really a simple enough job but as others have said in their replies " PLEASE BE CAREFUL OF THE HIGH VOLTAGES INSIDE THE TV " and be careful not to touch any of the capacitors on the PCB or you'll get a shock that will badly burn on both the entry and exit points of your body.
Good luck with it.
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Plus you will need a resistor to make the volume acceptable in your headphones, otherwise it will be too loud.
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StealthUK wrote:

...or for bonus points add a headphone volume control too.
--
jc

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On 5 Sep 2003 06:12:39 -0700, m_ snipped-for-privacy@hotmail.com (Michael Murray) wrote:

*** BEWARE CHARGE IS STORED IN A TV FOR A LONG TIME AFTER IT IS SWITCHED OFF, STAY AWAY FROM THE BACK OF THE TV TUBE ***
I did this to my cheap Matsui TV 15 years ago. No need for a switch the headphone socket cuts the sound to the speaker as it has 4 terminals. My TV died 5 years ago, sound played up just before it totally packed in, don't think it was connected with my mod.
Chris
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Is this just for your personal tv? If so you are probably ok with the advice from the other posts. But I do remember the technician at my university language lab telling me that when he did the tv's there, he had to install isolating transformers between the headphone socket and the speaker wires (I guess due to the possibility of live chassis).
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Millions of sets in use today dont have that, and do run with live chassis. It is not an outdated practice at all.
To connect a headphone to a chassis thats either live, or not live but not particularly well insulated from live, is a /really/ stupid idea.
Regards, NT
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N. Thornton wrote:

I just gave away a 10 year old JVC and that had an isolated chassis as does my new Sony and the two 5 year old small bedroom sets. BTW they all had/have headphone sockets too. How could they run modern electronics without a transformer of some kind?

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I'd agree that all the quality makes I've played with have been fully isolated.

Most quality makes do - and also AV connections, so they'd have to have an isolated chassis in practice.

If there were no external connections, you could use a form of auto transformer which is marginally cheaper?
--
*The hardness of the butter is proportional to the softness of the bread *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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IMHO that defeats the idea of an isolation transformer.
--
*If you lived in your car, you'd be home by now *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Dave Plowman wrote:

That depends on where you connect the EARTH wire. I was thinking of connecting it to EARTH. What about you? Live? Chassis? Why not be adventurous and connect it to that thick wire that goes into the side of the CRT?
Looking in an old RS catalogue I saw a 3W 1:1 speaker isolation transformer for about 5 quid. Put that before the internal speaker and you can use a switched 'phone socket.
If you're OK with a separate switch you could use a stepdown transformer after the internal speaker and do away with the resistors.
Roger.
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Perhaps you don't understand what isolation means? Would you also earth one side of a mains isolation transformer in a workshop?
--
*Don't use no double negatives *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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Dave Plowman wrote:

No but I'd earth the frame. Wouldn't you? WTF does that have to do with the problem of the live chassis TV? You can either have the headphone side of the transformer floating at some voltage determined by the leakage capacitance, or stick an earth lead on it (Not on the TV side!) and ensure that the sleeve is always at 0v.
Roger.
ps. Would you like to hear the story of Big Ears and Noddy's home-made electrostatic headphones?
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How long ago though?
TVs have moved on a bit in the last 50 years. It's very unlikely that a 14" portable would have a live chassis nowadays

--
geoff

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I've heard tell some sets with a crude SMPS do still have a 'live' chassis, although I've not come across one. I'd guess if its got any form of AV connections it should be safe, though.
--
*Why are they called apartments, when they're all stuck together? *

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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This was an el cheapo 14" colour portable, currys own brand, bought about 5 years ago. Chassis is at 120V above ground. Such designs are definitely still out there.
--
Tim Mitchell

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How are you measuring it? With a high impedance DVM you'll often get such readings as there could well be will be small value resistors etc from mains to chassis for RFI reasons. But the current they could supply is so little as not to be a safety hazard.
--
*I will always cherish the initial misconceptions I had about you

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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No, it really had some umph behind it, I was trying to make an audio out terminal. When I plugged something into it, I blew up a whole range of audio equipment, and nearly killed myself.
I later worked out the circuit diagram, it basically involved extra transformer windings and a 120V zener diode. The set is RF input only, no other connections (and now I know why).
--
Tim Mitchell

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