Laptop has small current coming from ground when plugged in.

[Shawn]

The laptop works fine but I can feel a small current going through my legs if it touchs my bare skin.

I checked with a multimeter and when I connect one end to any of the ground spots on the laptop and the other end to my finger I get a voltage of .3-.4v.

I just checked a different laptop and I don't get any current when doing the same test.

Ideas? I've already replaced RMAed one power adapter with no change.

 

[C1]

Does the notebook do the same thing when plugged in at at other physical locations such as a public library? If not, A possibility is that the home wiring is incorrect. Verify that the outlets are wired to code.

Use of a high quality (APC?) power strip/surge protector might help isolate the notebook.

I suppose another possibility is that you are experiencing a high voltage leakage associated with the CCFL circuitry.

 

[westom]

I checked with a multimeter and when I connect one end to any of the ground spots on the laptop and the other end to my finger I get a voltage of .3-.4v.

Route a three wire extension cord from a receptacle on another circuit (ideally the receptacle attached to the breaker box). Measure AC voltage from the laptop ground points to the safety ground on that extension cord. If you are feeling current, it should read many tens of volts. Your earlier meter readings probably were not making the appropriate connections.

If a problem is inside that laptop, then powering it from a bathroom or kitchen GFCI should trip that GFCO. If the laptop is defective.

Replacing its power supply would do nothing. Since the wall receptacle safety ground must always connect directly to grounds inside the laptop.

 

[Shawn]

The other laptop I was testing was connected to an outlet across the house. Decided to hook up the affected laptop to the same outlet as the other one and there is no current. There must be something wrong with that one outlet.

 

[bryanl]

There are RF filter capacitors connected between the AC lines and chassis ground, and when that ground isn't connected to earth ground through a 3-wire cord and grounded outlet, the chassis ground floats up half the line voltage.

 

[denis280]

The other laptop I was testing was connected to an outlet across the house. Decided to hook up the affected laptop to the same outlet as the other one and there is no current. There must be something wrong with that one outlet.

I did get some house and appt. with new ac plug put in.and the ground was not connected.

 

[Shawn]

I realized that I had it set to DC voltage. When I switched it to AC voltage I measured 44 volts AC coming from the laptop ground! However, I measured the negative terminal of the AC adaptor when it's not plugged into the laptop and it still measures 44 volts.

Here is what's really strange... when hooked up to the outlet across the house i measure around 17 volts AC.

I found my old AC adaptor (which I stopped using because the connection is lose) and I only get around 1 volt DC at either plug.

I guess this means both AC adaptors I got are defective? I still can't figure out the high AC voltage coming from adapter ground in my bedroom.

I connected the positive from the plug to the negative and got 117v, connected positive to ground and also got 117v. Connected negative to ground and no voltage. Brought extention cord from across the house and same result with connecting positive to ground of bedroom outlet and vice versa. Connected one ground to the other and no voltage.

Ideas?

 

[westom]

I realized that I had it set to DC voltage. When I switched it to AC voltage I measured 44 volts AC coming from the laptop ground!

Between the laptop ground and what? Every voltage measurement must always be between two well defined points. Every safety ground in the receptacle and DC ground inside a laptop must be considered completely different to make your numbers useful; to obtain useful advise.

 

[SecurityTheatre]

What do you mean you "feel" a current?

For you to feel it (and, in fact, for it to traverse your skin at all), either you are dripping wet, or you are dealing with an potentially dangerous current. The difference between being able to feel a household (120V) AC current (1mA rms minimum) and a shock severe enough that you lose voluntary control of your muscles (10mA rms) is pretty small.

Are you sure it's not air from the fan, or something else you're feeling?

 

[Shawn]

Between the laptop ground and what? Every voltage measurement must always be between two well defined points. Every safety ground in the receptacle and DC ground inside a laptop must be considered completely different to make your numbers useful; to obtain useful advise.

Between laptop ground and power outlet ground.

 

[Shawn]

What do you mean you "feel" a current?

For you to feel it (and, in fact, for it to traverse your skin at all), either you are dripping wet, or you are dealing with an potentially dangerous current. The difference between being able to feel a household (120V) AC current (1mA rms minimum) and a shock severe enough that you lose voluntary control of your muscles (10mA rms) is pretty small.

Are you sure it's not air from the fan, or something else you're feeling?

No, it is painful

 

[westom]

Between laptop ground and power outlet ground.

Plug for the power brick is a three prong type?

Seven or 15 volts should not be painful. You can feel maybe 60 volts. As stated here previously. Numbers you have provided are much lower. Would only cause a tingle at worst. If pain is significant, then perform everything and report back on what was recommended previously in this post.

 

[Shawn]

Plug for the power brick is a three prong type?

Seven or 15 volts should not be painful. You can feel maybe 60 volts. As stated here previously. Numbers you have provided are much lower. Would only cause a tingle at worst. If pain is significant, then perform everything and report back on what was recommended previously in this post.

Did that. See above. I am getting 44volts. I only feel a current when plugged in to the bedroom outlet. The power brick is a 3 prong type.

I think i figured it out. When testing the factory AC adapter the laptop ground is connected to the outlet ground, however with this new adapter they are not connected (no continuity).

 

[westom]

When testing the factory AC adapter the laptop ground is connected to the outlet ground, however with this new adapter they are not connected (no continuity).

Using a meter in ohms setting should confirm or measure the conductivity between the ground prong and at connector that plugs into the laptop. That connection should be near zero ohms on both adapters.

Current only in the bedroom outlet implies another problem. But again, further information is necessary.

Specifically, what happened when the laptop was powered from a GFCI protected outlet? Was that current felt during that GFCI powered connection? Or did trying to recreate that feel trip the GFCI (ie touch the laptop and metal parts of the sink)?

 

[Shawn]

The resistance is near zero for the old adapter and doesn't register for the faulty adapter (infinite). Also GFCI in bathroom does not trip when using faulty adapter. It is on the same circuit as bedroom.

 

[westom]

All that is good. Confirms you do not have a human safety problem. And have clearly identified the power brick (and not household wiring) for a defect.

 

[NutBucket]

I've seen this before with some older laptops at work. I'd set it down on an ESD mat and the ESD monitor would go nuts due to the current.

 

[Sheep221]

Laptops are not grounded, not at least via PE terminal found in receptacles, despite some chargers are grounded, it's only for them, charger is creating galvanical barrier between laptop and electrical network in building, which means the ground does not pass because the cable that goes to laptop only has 2 wires. Some connections that require ground such as D-SUB or USB are grounded via negative terminal instead. The problems you are experiencing are either of already mentioned CCFL interference or the charger is of very bad quality, mostly filters can be bad.

 

[DrPizza]

Just because it doesn't trip a GFI breaker doesn't mean that it's safe. A transformer isolates the load current - a GFI breaker doesn't see it.

And, if I had to take a guess as to why only on the bedroom outlet, try this OP: get an outlet tester; they're about $5. You plug them in and they light up for all sorts of conditions: reversed polarity, missing ground, etc. If it's only that one outlet, I'll bet there's a difference between that outlet and the other outlets. My best guess is that while that outlet has a ground plug, the ground is not actually grounded.

 

[Shawn]

Laptops are not grounded, not at least via PE terminal found in receptacles, despite some chargers are grounded, it's only for them, charger is creating galvanical barrier between laptop and electrical network in building, which means the ground does not pass because the cable that goes to laptop only has 2 wires. Some connections that require ground such as D-SUB or USB are grounded via negative terminal instead. The problems you are experiencing are either of already mentioned CCFL interference or the charger is of very bad quality, mostly filters can be bad.

What would cause CCFL interference? If that were it would it be possible that one AC adapter would have issue any another wouldn't?

 

[Sheep221]

What would cause CCFL interference? If that were it would it be possible that one AC adapter would have issue any another wouldn't?

Low quality electrical ballast that drives the lamps can be source of extra noise that you may feel as low voltage.
Anyway, your laptop has a metal case? Because it's the only reason there could be voltage leak on the case.

 

[Abwx]

There s a capacitor going from ground of the PSU back
to one pole of the main , hence there is systematicaly
an AC current running through this capacitor to ground
where it is sunked.


If it is not sunked then it means that the PSU ground
is not connected to the earth circuit , hence the 44V
measured between the laptop chassis and the earth
outlet.

 

[westom]

Laptops are not grounded, not at least via PE terminal found in receptacles, despite some chargers are grounded,

Then how do you explain the direct connection in this laptop? Some are. Some are not. If he has a safety ground prong, then a direct connection typically exists. Not always. Just mostly.

He has located the reason for feeling leakage electricity. One is missing a required ground.