Getting shocked by a laptop...is this normal?

[spodosaurus]

Hi all,

I was using a laptop that has s-video out. The s-video cable was plugged
into the TV. The laptop was plugged into mains power via its adapter.
When I went to plug the s-video into the back of the laptop my hand
(holding the s-video adapter end bit) brushed against a serial port on
the back and I got zapped. I tried without the s-video in hand, no zap,
and without touching the serial port, no zap. Is this normal? I relaise
there may be current coming from the TV down the s-video cable and went
through my hand into the serial port, or perhaps the other way. I cannot
imagine that this is a normal state of affairs, so I thought I'd ask the
experts here.

Ari

--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[Rod Speed]

I was using a laptop that has s-video out. The s-video cable was
plugged into the TV. The laptop was plugged into mains power via its
adapter. When I went to plug the s-video into the back of the laptop
my hand (holding the s-video adapter end bit) brushed against a
serial port on the back and I got zapped. I tried without the s-video
in hand, no zap, and without touching the serial port, no zap. Is
this normal? I relaise there may be current coming from the TV down
the s-video cable and went through my hand into the serial port, or
perhaps the other way. I cannot imagine that this is a normal state
of affairs, so I thought I'd ask the experts here.

It isnt unusual to get a tingle off a double insulated mains
powered device like a TV when the other side is grounded.

Nothing to worry about, its just the capacitor effect.

 

[Paul]

Hi all,

I was using a laptop that has s-video out. The s-video cable was plugged
into the TV. The laptop was plugged into mains power via its adapter.
When I went to plug the s-video into the back of the laptop my hand
(holding the s-video adapter end bit) brushed against a serial port on
the back and I got zapped. I tried without the s-video in hand, no zap,
and without touching the serial port, no zap. Is this normal? I relaise
there may be current coming from the TV down the s-video cable and went
through my hand into the serial port, or perhaps the other way. I cannot
imagine that this is a normal state of affairs, so I thought I'd ask the
experts here.

Ari

--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/

The definition of "normal" is, electrical devices are not intended to
shock people Therefore, you need to analyse what safety feature
has been defeated by your equipment configuration or by a malfunction.

There is an article here, about standards in various countries.

http://en.wikipedia.org/wiki/Mains_power_plug

Something is not normal here, and needs to be fixed. For each device
that has a safety ground (three prong plug), is the safety ground
intact ? Are there any two prong only plugs in the path, that have
broken the path to the safety ground ? Either a safety ground is
missing, or something that is nominally insulated, is now leaking.
Maybe the fault is with the wall adapter for the laptop.

In North America, you can get devices like this. By means of some
neon bulbs inside the test plug, this device can identify if the
wiring of an outlet is correct. Perhaps you could get one of
these, as a quick means of verifying that the AC outlet(s) in your
residence are correct (at least for all the outlets being used
in the faulty situation).

http://www.tequipment.net/AEMCOT1.html
http://www.tequipment.net/ProductImages/AEMC/OT-1.jpg

On a desktop computer at least, once the safety ground pin is broken
off, the computer becomes a source of a small amount of leakage current,
from the EMI filter on the AC entry point to the PSU. At least one
poster here was receiving a shock from a computer, due to having no
safety ground pin on the wiring.

Paul

 

[spodosaurus]

It isnt unusual to get a tingle off a double insulated mains
powered device like a TV when the other side is grounded.

Nothing to worry about, its just the capacitor effect.

Thanks Rod. Given that it's making a high pitched noise, reminiscent of
a modem or the sound effects for computers in 1980s B-grade movies, and
the manufacturer is going to be sending someone around to fix the laptop
screen hinge as well as replace the motherboard (to stop the noise...it
sounds more like it's coming from the miniPCI card or the hard drive,
but not at all like a bearing noise) I thought I should check and see.
If something else needed to be replaced to fix the zapping and the
noise, I'd rather they do that first instead of after openning the
laptop two or three times and replacing random parts.

Any ideas about what could be causing the sound?


--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[spodosaurus]

Wow Paul that was a lot to take in. Both the television and the laptop's
plugs are fine. I may have been in contact with the metal end of the
s-video connector when I brushed against the metal serial port.

Given that it's making a high pitched noise, reminiscent of a modem or
the sound effects for computers in 1980s B-grade movies, and the
manufacturer is going to be sending someone around to fix the laptop
screen hinge as well as replace the motherboard (to stop the noise...it
sounds more like it's coming from the miniPCI card or the hard drive,
but not at all like a bearing noise) I thought I should check and see
about the shocks.

If something else needed to be replaced to fix the zapping and the
noise, I'd rather they do that first instead of after openning the
laptop two or three times and replacing random parts.

Any ideas about what could be causing the sound?

I was asked in the library the other day if my laptop was one of the
kinds that was going to be a fire hazard after it started making the
noise. It's faint in a normal environment, but in a library it is
noticeable.

Ari

--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[Rod Speed]

Rod Speed wrote

Thanks Rod. Given that it's making a high pitched noise, reminiscent
of a modem or the sound effects for computers in 1980s B-grade
movies, and the manufacturer is going to be sending someone around to
fix the laptop screen hinge as well as replace the motherboard (to stop the noise...it sounds more
like it's coming from the miniPCI card or the hard drive, but not at all like a bearing noise) I
thought I should check and see.

Yeah, understandable with that noise there too.

The short story with the tingle, if that is all it is, is that there is
nothing much you can do about it with the svideo connection.
With the antenna connection you can use a balun, but its more
complicated with the svideo connection. Dont worry about it.

If something else needed to be replaced to fix the zapping and the noise, I'd rather they do that
first instead of after openning the laptop two or three times and replacing random parts.

Yeah, and if the monkey isnt aware of the tingle problem with
double insulated devices like TVs, it wont help at all anyway.

Any ideas about what could be causing the sound?

Noises are notoriously hard to describe. Nothing springs to
mind, but that might be different if you could record the sound.

It might be the hard drive recalibrating, and that is real bad news.

It might just be a fan bearing, tho that seems unlikely given
that you say that it doesnt sound like a bearing noise.

You can sometimes get a fault in the audio system that produces noises.

 

[Rod Speed]

The definition of "normal" is, electrical devices are not intended to
shock people Therefore, you need to analyse what safety feature
has been defeated by your equipment configuration or by a malfunction.

There is an article here, about standards in various countries.

http://en.wikipedia.org/wiki/Mains_power_plug

Something is not normal here, and needs to be fixed.

Not necessarily if its just the tingle that you
get with double insulated devices like TVs.

For each device that has a safety ground
(three prong plug), is the safety ground intact ?

Most stuff like TVs are double insulated now, so no earth line.

Are there any two prong only plugs in the path, that have
broken the path to the safety ground ? Either a safety ground is
missing, or something that is nominally insulated, is now leaking.

Or its just the usual effect with double insulated devices.

 

[Davy]

Static build up on the TV passing through to the laptop via the leads,
it could of course be leakage current from the switch-mode section or
flyback section... these are usually taken care of by pretty high
value resistors strapped across the non-isolated supply, typically
8.2M ohms which passes any leakage or static build up on the TV side
back down the mains.

Between the main TV section and the primary unit there is a safety
barrier - a certain amount of space between the two sections to
prevent flash-over due to HV or static discharges etc.

If the board becomes heavily contaminated this safety zone could
easily breakdown making the discharge resistors useless, this would
break the isolation between between the mains or the isolated
section.

If you used a PAT tester the TV would most probably show any leakage
presence between the plug and any bare surfaces such as a socket or
speaker grille.

If its static or leakage it just shouldn't be there. It is incorrect
to say that these things should not be ignored incase any injury or
damage should occur.

Davy

 

[spodosaurus]

Yeah, understandable with that noise there too.

The short story with the tingle, if that is all it is, is that there is
nothing much you can do about it with the svideo connection.
With the antenna connection you can use a balun, but its more
complicated with the svideo connection. Dont worry about it.


Yeah, and if the monkey isnt aware of the tingle problem with
double insulated devices like TVs, it wont help at all anyway.


Noises are notoriously hard to describe. Nothing springs to
mind, but that might be different if you could record the sound.

It might be the hard drive recalibrating, and that is real bad news.

It might just be a fan bearing, tho that seems unlikely given
that you say that it doesnt sound like a bearing noise.

You can sometimes get a fault in the audio system that produces noises.

It's intermittent, usually and I can hear the hard drive making its
normal grumbling noises in bursts when it's happening. The last time it
was doing it (last night) I was watching a full screen power point
slideshow for work training. When I would switch between slides, both
the grumbling and the high pitched noise would stop.

Ari

--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[spodosaurus]

It's intermittent, usually and I can hear the hard drive making its
normal grumbling noises in bursts when it's happening. The last time it
was doing it (last night) I was watching a full screen power point
slideshow for work training. When I would switch between slides, both
the grumbling and the high pitched noise would stop.

Ari

PS- Hitachi drive tool, after a full scan, says the drive is okay. It's
bloody hot though: the bottom of the laptop is hot to the touch under
the drive panel.

Ari

--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[spodosaurus]

PS- Hitachi drive tool, after a full scan, says the drive is okay. It's
bloody hot though: the bottom of the laptop is hot to the touch under
the drive panel.

Ari

Okay, replacing the motherboard did nothing, but it did give the tech
some time to remove other cards and recreate the noise (we even got a
new type of high pitched noise this time, we both thought it was coming
from the other's mobile phone). Looks to be the hard drive, getting
replaced tomorrow. I never like getting 'new' things at the end of a
warranty, especially motherboards. MI think my old board was fine, and
if it was it probably would have remained fine for a while. However, a
new board that dies a month out of warranty is very agitating
....especially with laptops and the cost of replacement parts!

--
spammage trappage: remove the underscores to reply
Many people around the world are waiting for a marrow transplant. Please
volunteer to be a marrow donor and literally save someone's life:
http://www.abmdr.org.au/
http://www.marrow.org/

 

[Rod Speed]

Okay, replacing the motherboard did nothing, but it did give the tech
some time to remove other cards and recreate the noise (we even got a
new type of high pitched noise this time, we both thought it was
coming from the other's mobile phone). Looks to be the hard drive,
getting replaced tomorrow.

Yeah, that's certainly possible.

I never like getting 'new' things at the end of a warranty, especially motherboards. MI think my
old board was fine, and if it was it probably would have remained fine for a while.

Yeah, it shouldnt die. Understandable that he didnt want to
swap the original back in tho time wise. I normally do that myself.

However, a new board that dies a month out of warranty is very
agitating ...especially with laptops and the cost of replacement parts!

Yeah, that's the main downside with laptops.