Shocked through stereo headphones in computer jack?

[Brett Shoelson]

Hi,
I just had the unpleasant experience of getting shocked through a pair of
Sony headphones plugged (via a Radio Shack extension) into the speaker port
of my computer. I wondered if anyone has ever heard of this happening
before? Is this the result of an impedance mismatch in the cables, or might
there be a fault in the headphones or jack? I'm a bit nervous about wearing
these things again.
Thanks,
Brett

 

[Tim Wescott]

I get shocked any time I listen to AM talk radio, headphones or no.

Seriously, what kind of shock was it? It's probably not the headphones, and
probably would have happened just from touching a metal part of the computor
case. If it was a dry day and you got a single "spap!!" then it was
probably electrostatic discharge. If it a continuous shock with that ol'
60Hz feel then there's a fault in your power supply or electrical wiring
that on a bad day will be fatal.

If you suspect a continuous shock you should start by checking your outlets
(they _are_ three-wire, right?). You can get inexpensive little outlet
testers at the Rat Shack or at home centers -- they have three little lights
that show the status of the outlet. Once you know that's good, take a
multimeter and plug it into the ground hole of the outlet (it's OK, he says,
keeping one hand behind his back...). Now measure the AC voltage between
that ground and your computor case. If it's anything over a few millivolts
then you have a problem with the computor.

"Brett Shoelson" <shoelson@helix.nih.gov> wrote in message
news:YnVPb.547$Er.32008@mencken.net.nih.gov...

Hi,
I just had the unpleasant experience of getting shocked through a pair of
Sony headphones plugged (via a Radio Shack extension) into the speaker
port
of my computer. I wondered if anyone has ever heard of this happening
before? Is this the result of an impedance mismatch in the cables, or
might
there be a fault in the headphones or jack? I'm a bit nervous about
wearing
these things again.
Thanks,
Brett

 

[Walter Harley]

"Tim Wescott" <tim@wescottnospamdesign.com> wrote in message
news:1010direkq1cc40@corp.supernews.com...

Seriously, what kind of shock was it? It's probably not the headphones,
and
probably would have happened just from touching a metal part of the
computor
case. If it was a dry day and you got a single "spap!!" then it was
probably electrostatic discharge. If it a continuous shock with that ol'
60Hz feel then there's a fault in your power supply or electrical wiring
that on a bad day will be fatal.

The story is that's how Keith Relf, lead singer for the Yardbirds, died. Of
course, it wasn't a computer that his headphones were plugged into.

If you suspect a continuous shock you should start by checking your
outlets
(they _are_ three-wire, right?). You can get inexpensive little outlet
testers at the Rat Shack or at home centers -- they have three little
lights
that show the status of the outlet. Once you know that's good, take a
multimeter and plug it into the ground hole of the outlet (it's OK, he
says,
keeping one hand behind his back...). Now measure the AC voltage between
that ground and your computor case. If it's anything over a few
millivolts
then you have a problem with the computor.

Mind you, Tim's talking about measuring to a *bare metal* part of the
computer case - like a screw - not a plastic or painted part. Probably
obvious, but thought I'd mention it.

And depending on your meter, and a few other factors, it wouldn't be
surprising to see as much as half a volt.

By the way, just because an outlet has three holes doesn't mean it's
grounded. It could have been defectively installed (found one of those in
my own house, even after hiring an electrician to bring everything up to
code when I bought the house); or the ground wiring could have become
defective over time. It's not even unusual to find that someone has
installed three-wire outlets into a two-wire electrical system, just for
"convenience" or to fool a buyer. Of course, it's completely illegal and
quite unsafe.

 

[Brett Shoelson]

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:1010iqlkcb5gb21@corp.supernews.com...

"Tim Wescott" <tim@wescottnospamdesign.com> wrote in message
news:1010direkq1cc40@corp.supernews.com...
Seriously, what kind of shock was it? It's probably not the headphones,
and
probably would have happened just from touching a metal part of the
computor
case. If it was a dry day and you got a single "spap!!" then it was
probably electrostatic discharge. If it a continuous shock with that
ol'
60Hz feel then there's a fault in your power supply or electrical wiring
that on a bad day will be fatal.

The story is that's how Keith Relf, lead singer for the Yardbirds, died.
Of
course, it wasn't a computer that his headphones were plugged into.



If you suspect a continuous shock you should start by checking your
outlets
(they _are_ three-wire, right?). You can get inexpensive little outlet
testers at the Rat Shack or at home centers -- they have three little
lights
that show the status of the outlet. Once you know that's good, take a
multimeter and plug it into the ground hole of the outlet (it's OK, he
says,
keeping one hand behind his back...). Now measure the AC voltage
between
that ground and your computor case. If it's anything over a few
millivolts
then you have a problem with the computor.

Mind you, Tim's talking about measuring to a *bare metal* part of the
computer case - like a screw - not a plastic or painted part. Probably
obvious, but thought I'd mention it.

And depending on your meter, and a few other factors, it wouldn't be
surprising to see as much as half a volt.

By the way, just because an outlet has three holes doesn't mean it's
grounded. It could have been defectively installed (found one of those in
my own house, even after hiring an electrician to bring everything up to
code when I bought the house); or the ground wiring could have become
defective over time. It's not even unusual to find that someone has
installed three-wire outlets into a two-wire electrical system, just for
"convenience" or to fool a buyer. Of course, it's completely illegal and
quite unsafe.

Thanks, Tim and Walter. I will test the potential difference between the
case (yes, I know enough to measure from the metal part) and ground. And
I'll verify the connections of the plug. (It would be surprising if the
problem were in the wiring of the plug, though, as I am sitting in a
relatively newly refurbished lab in the National Institutes of Health.) The
discharge I experienced seemed to be a quick series of crisp pops. I somehow
manage to build up static charge all day long here, and am constantly zapped
when I touch doorknobs, etc. But it's unsettling when the discharge is
across one's ears!
Regards,
Brett

 

[Tim Wescott]

"Quick series of crisp pops" sounds much more like static discharge than an
AC wiring problem. I suspect that you build up charge until it exceeds the
breakdown voltage between your headphone and your head, then it goes off.

I hope you don't work around volatile flammible solvents, or sensitive
electronics.

You can get antistatic chair mats (and antistatic chairs, for that matter)
that prevent this. You may want to investigate (or wear an electronics
style anti-static strap).

"Brett Shoelson" <shoelson@helix.nih.gov> wrote in message
news:z4YPb.550$Er.31978@mencken.net.nih.gov...

-- snip --

Thanks, Tim and Walter. I will test the potential difference between the
case (yes, I know enough to measure from the metal part) and ground. And
I'll verify the connections of the plug. (It would be surprising if the
problem were in the wiring of the plug, though, as I am sitting in a
relatively newly refurbished lab in the National Institutes of Health.)
The
discharge I experienced seemed to be a quick series of crisp pops. I
somehow
manage to build up static charge all day long here, and am constantly
zapped
when I touch doorknobs, etc. But it's unsettling when the discharge is
across one's ears!
Regards,
Brett

 

[Walter Harley]

"Brett Shoelson" <shoelson@helix.nih.gov> wrote in message
news:z4YPb.550$Er.31978@mencken.net.nih.gov...

I'll verify the connections of the plug. (It would be surprising if the
problem were in the wiring of the plug, though, as I am sitting in a
relatively newly refurbished lab in the National Institutes of Health.)

You have much more faith in electricians than I do. Remember, for every
trained, skilled, attentive professional electrician, there's an apprentice
working on one side of him/her, and a burnt-out, overworked,
soon-to-be-ex-electrician on the other

But it does sound like an innocent, if alarming, static discharge.
Especially if you're on the east coast in January.

 

[Dave Cole]

in article YnVPb.547$Er.32008@mencken.net.nih.gov, Brett Shoelson at
shoelson@helix.nih.gov wrote on 1/22/04 13:20:

Hi,
I just had the unpleasant experience of getting shocked through a pair of
Sony headphones plugged (via a Radio Shack extension) into the speaker port
of my computer. I wondered if anyone has ever heard of this happening
before? Is this the result of an impedance mismatch in the cables, or might
there be a fault in the headphones or jack? I'm a bit nervous about wearing
these things again.
Thanks,
Brett

Was it a ^single^ snap or a 60 hz ^buzz^. Single snap would more than

likely be static on you shocking the headphones.

HTH
Dave Cole

 

[William P.N. Smith]

"Brett Shoelson" <shoelson@helix.nih.gov> wrote:

I somehow
manage to build up static charge all day long here, and am constantly zapped
when I touch doorknobs, etc.

Try wearing a heel strap. 3M makes some disposable ones that are
quite nice. IMHO, the non-disposable ones are annoying...
http://www.staticspecialists.com/personalgrounding.htm#shoe

--
William Smith
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[Brett Shoelson]

"Brett Shoelson" <shoelson@helix.nih.gov> wrote in message
news:YnVPb.547$Er.32008@mencken.net.nih.gov...

Hi,
I just had the unpleasant experience of getting shocked through a pair of
Sony headphones plugged (via a Radio Shack extension) into the speaker
port
of my computer. I wondered if anyone has ever heard of this happening
before? Is this the result of an impedance mismatch in the cables, or
might
there be a fault in the headphones or jack? I'm a bit nervous about
wearing
these things again.
Thanks,
Brett

Hi everyone,
Thanks for the replies. The shock was a quick series of snaps--maybe 3 of
them in rapid succession. Not a continuous jolt...and yes, this is the east
coast in January. So I've added an additional grounding wire to the case of
my computer, and ran a bare copper wire to ground across my desk in front of
my keyboard. I'll post again if I experience (and survive) another one of
these.
Regards,
Brett

 

[Michael A. Terrell]

Brett Shoelson wrote:

Hi everyone,
Thanks for the replies. The shock was a quick series of snaps--maybe 3 of
them in rapid succession. Not a continuous jolt...and yes, this is the east
coast in January. So I've added an additional grounding wire to the case of
my computer, and ran a bare copper wire to ground across my desk in front of
my keyboard. I'll post again if I experience (and survive) another one of
these.

Connect a one megohm resistor from ground to a piece of metal and
touch it when you walk up to your desk to drain off the static charge,
without getting shocked. They used to sell this under the name of "Touch
me first!" in the early days of personal computers. Also, if there is a
lot of static, the janitors should use either special floor wax that
dissipates the charge, or spray a thin mixture of fabric softener on the
tile and carpets in the winter months.

--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida

 

[Remove _ for valid addres]

In article <YnVPb.547$Er.32008@mencken.net.nih.gov>, Brett Shoelson wrote:

Hi,
I just had the unpleasant experience of getting shocked through a pair of
Sony headphones plugged (via a Radio Shack extension) into the speaker port
of my computer. I wondered if anyone has ever heard of this happening
before? Is this the result of an impedance mismatch in the cables, or might
there be a fault in the headphones or jack? I'm a bit nervous about wearing
these things again.
Thanks,
Brett

Happened to me the first time I got a CD-Rom on my computer. I plugged
the headphones in, started listening, then put my finger to the screen
(to clean a bit of dirt off it). Zap in my ears! Took me another zap
before I realised where the static comes from! I tend to use a speaker
these days. ;-)

Mike.