Tv - 75v exposed conductive parts

[gazdkw82]

mother inlaw says - I keep getting a shock of the back of the tv when I try and move it to turn the plug off.

It’s a wall mounted tv in the kitchen.

I thought initially it must be just static but told her I’d have a look. As it happens, every screw, or exposed conductive part on the tv is measuring at 75v.

I only had a voltage indicator with me as We went for dinner.

All I did was measure between any conductive part and the Earth witchin the socket.

I thought asking my tutor at college would help but he said he doesn’t know because TVs are double insulated and have no connection to Earth. In fact the screws themselves are usually screwed into a plastic housing.

Any ideas?

 

[Pete999]

mother inlaw says - I keep getting a shock of the back of the tv when I try and move it to turn the plug off.

It’s a wall mounted tv in the kitchen.

I thought initially it must be just static but told her I’d have a look. As it happens, every screw, or exposed conductive part on the tv is measuring at 75v.

I only had a voltage indicator with me as We went for dinner.

All I did was measure between any conductive part and the Earth witchin the socket.

I thought asking my tutor at college would help but he said he doesn’t know because TVs are double insulated and have no connection to Earth. In fact the screws themselves are usually screwed into a plastic housing.

Any ideas?

What type of instrument did you use to measure the voltage?

 

[gazdkw82]

A voltage indicator.

It has display to display exact voltage

 

[Pete999]

A voltage indicator.

It has display to display exact voltage

Do you have access to a decent analog voltmeter? a voltage indicator wont be very accurate, in my opinion.

 

[David Prosser]

Does the voltage change with the TV unplugged ?
Is the mounting bracket screwed to the wall, maybe gone through a cable.

 

[gazdkw82]

I didn’t try it unplugged but I tested the bracket an numerous points and couldn’t see anything, however the bracket is mainly coated.

Yeh I have a multimeter so I’ll take that next time and do some more measurements

 

[Pete999]

Does the voltage change with the TV unplugged ?
Is the mounting bracket screwed to the wall, maybe gone through a cable.

If you're right DAvid, would an IR test on the circuit feed the TV be in order?

 

[David Prosser]

??? Would be better off trying to identify the circuit that has been damaged. If indeed the errant voltage is coming through that way.

 

[gazdkw82]

I’ll do some investigation. I’ll check supply and Cables for tv

 

[Marvo]

As mentioned try the same test with an analogue tester or a digital tester with a LoZ adapter or setting. Also does the TV have a coaxial aerial cable plugged into it? If so unplug any antenna cables and try the test again, sometimes an amplifier or LNB supply upstream on the signal cables can feed back a voltage onto the ungrounded chassis.

 

[gazdkw82]

OK, had another look today as I have my multimeter with me.

Narrowed it down to the aerial which is fed from a booster in the loft. Got a reading of 101v dc from the aerial.

Iv done some research and it seems these boosters can do this. I may just bond the aerial to Earth in the loft.

Would that be an ideal solution? Would it cause the rcd to play up?