I have a portable TV which I want to add a headphone socket to.
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.
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.
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.
*** 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.
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).
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.
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?
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
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
ps. Would you like to hear the story of Big Ears and Noddy's home-made
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 email@example.com London SW 12
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).
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