Earthing in TV

I just bought a new TV and found

  1. it had no earthing pin in its power cable (only Phase and Neutral were there)

  1. its audio GND (accessible from RCA connector) showed me presence of voltage when I touched a screw-driver-cum-mains-tester to it.

  2. I tried to touch the audio GND, but did not get a shock.

First, why was the TV GND floating (meaning, not earthed) ?

Can I safely connect my PC audio output to TV audio input ?

What if I manually earthed the TV GND ?

Thanks Mike

Reply to
siliconmike
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externally

reference is

One thing that comes to mind is that the TV power connector might not have an earthing pin to protect it from lightning striking the antenna. Since the whole TV electronics is floating, lightning voltages (which are relative to earth) might prove to be less damaging.

Any responses to my other questions below..?

Neutral

of

Reply to
siliconmike

Because it's chassis ground, or signal common, neither of which is Earth ground. (obviously, because the set is fully isolated and has no Earth pin).

Probably. But why?

Don't. It will cause ground loops, and introduce problems that you don't have now. This is an entire subject of study - try

formatting link

You're welcome.

Cheers! Rich

Reply to
Rich Grise

More likely capacitively coupled or ordinary electromagnetic induction a la antenna.

Cheers! Rich

Reply to
Rich Grise

First some definitions and concepts. Then some simple experiments.

Your are confusing earth ground with something called safety ground. Your TV has no safety ground connection because a third ground inside the TV is isolated - a floating ground. A voltage difference between a floating ground and safety ground is undefined. It may or may not harm you if you touch both simultaneously.

In the meantime, anything conductive outside of that TV must be galvanically isolated from floating ground. Isolated does not mean no electrical conductivity. Isolated means minimal electrical connection.

Two tests for sufficient human safety. First, plug the TV into a working (and pre-tested) GFCI outlet. Connect a jumper cable from that audio ground to the safety ground (ie a screw holding the wall receptacle cover plate). This test should not trip the GFCI. Some current will pass from that audio ground into wall receptacle. Current must be so low as to not trip GFCI.

Second, measure that leakage current using the meter set for AC current. Measure well less than 150 microamps (0.15 milliamps) from audio ground to wall receptacle 'safety ground'. Some leakage current should be measured. Current so low as to not threaten human life and not trip the GFCI. Galvanic isolation does not mean zero current. It means minimal leakage current.

BTW, the safety ground > I just bought a new TV and found

Reply to
w_tom

Earth

Earth

Sure, I know that, but what reasons did they have in not introducing the Earth pin to short the signal common to the Earth..?

Reply to
siliconmike

Right, thats understood. Now since the TV has 2000W exceptionally good audio amplifier, I would like to connect audio out from my PC to audio in of TV.

As I understand, your mentioned example current (0.15 mA) would flow from the TV signal ground to the Sound Card GND tracks, then to the mother board GND tracks, then to the POWER SUPPLY gnd wire, then to the WALL OUTLET safety GND.. (PC has earth pin)

Although this current is too small, I presume it is not worth taking a risk. Moreover, if some static phenomenon occurs in the TV, it might damage the PC!

Reply to
siliconmike

good

audio

Samsung. (I'm in India)

Reply to
siliconmike

If wire is grounded via computer and soundcard (a common mode connection), then no static problem exists. None.

Static is not created by the TV. Voltage leakage from a floating ground, as described earlier, may be created by the TV. That leakage must be so low as to not harm humans, which means that leakage is too low to harm electronics. If worried, then make the connections before powering computer and TV. A redundant layer of protection.

Earlier noted was that a defective TV (galvanic isolation failed) might conduct current through you when you touch both audio ground and safety ground simultaneously. But then this is what those two experiments do. They confirm the defect does not exist.

I d> Right, thats understood. Now since the TV has 2000W exceptionally good

Reply to
w_tom

Has the brand of the TV been mentioned?

--
John Miller
email domain: n4vu.com; username: jsm(@)
Reply to
John Miller

CS-29T10PA

Man this TV rocks! Now I don't need to go to theatre. I put it 10 ft from me and watch DVDs.. Its 29".. And cost is (in US $) $600..

Reply to
siliconmike

Which model Samsung TV has 2000W output??

Ken

Reply to
Ken Taylor

Even if they're using Peak Music Power, India must use much smaller watts than the rest of the world.

--
Peter Bennett, VE7CEI  
peterbb4 (at) interchange.ubc.ca  
 Click to see the full signature
Reply to
Peter Bennett

Sure I know that, but with this TV I bet one could throw a dance party. The sound is beautiful, and of course loud enough.

And while a

it.

Its perfect for the price I guess.

audio

it

some

unless

response.

Reply to
siliconmike

Peter, why not do a self analysis before posting sarcastic comments for a nation of 1 billion ? I wouldn't be surprised if someone from India made you feel not very comfortable for what you just wrote.

Reply to
siliconmike

that

bit

Well I'm not sure who should be ashamed of surfing abilities, but here are the specs on Samsung's website found in less than a minute.

formatting link

Reply to
siliconmike

Here's what I did: Connected TV Signal earth to safety earth directly by a thick cable (16 SWG x 10) and then connected the PC to the TV. The tester stopped showing any presence of voltage on the TV signal earth, and the reception is ok. PC is ok.

Reply to
siliconmike

"Peak Music Power" is a term you need to become familiar with. And while a

29" TV is swell, it's hardly out-of-this-world. Anyway, glad you like it. And in answer to the original question, yes you can connect your PC audio output to the TV safely (assuming the PC is safe to start with). If it really concerns you that there may be a problem you could hunt out some audio isolation transformers to put between the PC and the TV, but unless you paid a reasonable amount of money it would degrade your audio response.

Ken

Reply to
Ken Taylor

Temporarily disconnect computer and ground cable. Measure AC current from audio ground to that new safety ground wire. Current should be on the order of less than 1 milliamp. Unlike the experiment with safety ground wire, this test actually reports something useful.

Of course that grounding cable will eliminate voltage. Wire eliminating voltage tells us nothing useful. But is that voltage created by a leakage that is too large or by a leakage that is acceptable? You still have not answered a question that determines whether a threat to computer, et al exists.

If your meter does not have an AC amperage option, then connect audio ground to safety ground via a 10K ohm resistor. If the leakage is 150 microamps, then AC voltage across that resistor will be 1.5 volts. If the voltage is less, then the leakage (and need for safety ground wire) is irrelevant. If voltage across resistors is more, than your TV may be a threat to computer and human life.

If leakage is less than 150 uamps, then even a wire about the size of a human hair would have been sufficient to ground out the leakage.

Aga> Here's what I did: Connected TV Signal earth to safety earth directly

Reply to
w_tom

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