Shock from USB printer cable

K

Keith Weisshar

Guest
I felt a small shock when I touched the USB connector from the Canon Pixma
IP1500 printer and the grounded PC case at the same time. It's not a 60hz
AC type of shock but is felt as very brief pulses of approximately 2-3
pulses per second when printer is in off mode. These pulses are faster if
the printer is turned on. I put a neon tester between the USB cable and the
PC ground and it glew continuously but could not see the pulses on the neon
tester. Although the neon tester glew continuously, why did I only feel a
series of short pulses about 2-3 times per second. The shock feels like a
couple of milliamps through the finger.
 
Yikes! I suspect a defect in the power supplies of the PC or the printer or
the wiring of the outlets they are plugged into.

I DO NOT THINK IT IS SAFE TO CONNECT THEM TOGETHER. Please don't.

I'm guessing they both have 3-wire power cords and are plugged into
different outlets, and one of the outlets is not grounded properly. Is that
the case?

Or the printer has a 2-wire power cord and has a defect in its power supply.
Again, one of the outlets is probably not wired properly.

You can get a little tester with 3 neon lamps in it which you plug into an
outlet to check that the correct side is grounded. I urge you to do so.

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:yAG0d.1311$yJ3.282@trndny08...
I felt a small shock when I touched the USB connector from the Canon Pixma
IP1500 printer and the grounded PC case at the same time. It's not a 60hz
AC type of shock but is felt as very brief pulses of approximately 2-3
pulses per second when printer is in off mode. These pulses are faster if
the printer is turned on. I put a neon tester between the USB cable and
the
PC ground and it glew continuously but could not see the pulses on the
neon
tester. Although the neon tester glew continuously, why did I only feel a
series of short pulses about 2-3 times per second. The shock feels like a
couple of milliamps through the finger.
Click to expand...
 
The computer is grounded but the printer is not. The printer has a
non-polarized plug. I tried reversing the printer plug and the result was
the same. Both the computer and printer is plugged into the UPS unit which
has a built-in building wiring fault light but this light is off. The
computer has the third prong intact. The outlet tester indicates correct
polarity. Many SMPS have the ground side connected through a small
capacitor to the negative DC side of the AC line rectifier. I have the
printer connected to the computer and am able to print without any trouble.
There is only a tiny spark when touching the USB cable to the PC case.

----- Original Message -----
From: "Michael A. Covington" <look@ai.uga.edu.for.address>
Newsgroups: sci.electronics.misc
Sent: Saturday, September 11, 2004 2:38 PM
Subject: Re: Shock from USB printer cable


Yikes! I suspect a defect in the power supplies of the PC or the printer
or
the wiring of the outlets they are plugged into.

I DO NOT THINK IT IS SAFE TO CONNECT THEM TOGETHER. Please don't.

I'm guessing they both have 3-wire power cords and are plugged into
different outlets, and one of the outlets is not grounded properly. Is
that
the case?

Or the printer has a 2-wire power cord and has a defect in its power
supply.
Again, one of the outlets is probably not wired properly.

You can get a little tester with 3 neon lamps in it which you plug into an
outlet to check that the correct side is grounded. I urge you to do so.

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:yAG0d.1311$yJ3.282@trndny08...
I felt a small shock when I touched the USB connector from the Canon
Pixma
IP1500 printer and the grounded PC case at the same time. It's not a
60hz
AC type of shock but is felt as very brief pulses of approximately 2-3
pulses per second when printer is in off mode. These pulses are faster
if
the printer is turned on. I put a neon tester between the USB cable and
the
PC ground and it glew continuously but could not see the pulses on the
neon
tester. Although the neon tester glew continuously, why did I only feel
a
series of short pulses about 2-3 times per second. The shock feels like
a
couple of milliamps through the finger.
Click to expand...
"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in message
news:41434799$1@mustang.speedfactory.net...
Yikes! I suspect a defect in the power supplies of the PC or the printer
or
the wiring of the outlets they are plugged into.

I DO NOT THINK IT IS SAFE TO CONNECT THEM TOGETHER. Please don't.

I'm guessing they both have 3-wire power cords and are plugged into
different outlets, and one of the outlets is not grounded properly. Is
that
the case?

Or the printer has a 2-wire power cord and has a defect in its power
supply.
Again, one of the outlets is probably not wired properly.

You can get a little tester with 3 neon lamps in it which you plug into an
outlet to check that the correct side is grounded. I urge you to do so.

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:yAG0d.1311$yJ3.282@trndny08...
I felt a small shock when I touched the USB connector from the Canon
Pixma
IP1500 printer and the grounded PC case at the same time. It's not a
60hz
AC type of shock but is felt as very brief pulses of approximately 2-3
pulses per second when printer is in off mode. These pulses are faster
if
the printer is turned on. I put a neon tester between the USB cable and
the
PC ground and it glew continuously but could not see the pulses on the
neon
tester. Although the neon tester glew continuously, why did I only feel
a
series of short pulses about 2-3 times per second. The shock feels like
a
couple of milliamps through the finger.
Click to expand...
 
Printer only has two-wire plug while the computer has three-wire plug.

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:I%I0d.204$W73.52@trndny03...
It's a brand new model of the printer that just came out last month.

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:4YI0d.4842$sX2.3757@trndny09...
The computer is grounded but the printer is not. The printer has a
non-polarized plug. I tried reversing the printer plug and the result
was
the same. Both the computer and printer is plugged into the UPS unit
which
has a built-in building wiring fault light but this light is off. The
computer has the third prong intact. The outlet tester indicates
correct
polarity. Many SMPS have the ground side connected through a small
capacitor to the negative DC side of the AC line rectifier. I have the
printer connected to the computer and am able to print without any
trouble.
There is only a tiny spark when touching the USB cable to the PC case.

----- Original Message -----
From: "Michael A. Covington" <look@ai.uga.edu.for.address
Newsgroups: sci.electronics.misc
Sent: Saturday, September 11, 2004 2:38 PM
Subject: Re: Shock from USB printer cable


Yikes! I suspect a defect in the power supplies of the PC or the
printer
or
the wiring of the outlets they are plugged into.

I DO NOT THINK IT IS SAFE TO CONNECT THEM TOGETHER. Please don't.

I'm guessing they both have 3-wire power cords and are plugged into
different outlets, and one of the outlets is not grounded properly.
Is
that
the case?

Or the printer has a 2-wire power cord and has a defect in its power
supply.
Again, one of the outlets is probably not wired properly.

You can get a little tester with 3 neon lamps in it which you plug
into
an
outlet to check that the correct side is grounded. I urge you to do
so.

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:yAG0d.1311$yJ3.282@trndny08...
I felt a small shock when I touched the USB connector from the Canon
Pixma
IP1500 printer and the grounded PC case at the same time. It's not
a
60hz
AC type of shock but is felt as very brief pulses of approximately
2-3
pulses per second when printer is in off mode. These pulses are
faster
if
the printer is turned on. I put a neon tester between the USB cable
and
the
PC ground and it glew continuously but could not see the pulses on
the
neon
tester. Although the neon tester glew continuously, why did I only
feel
a
series of short pulses about 2-3 times per second. The shock feels
like
a
couple of milliamps through the finger.





"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in message
news:41434799$1@mustang.speedfactory.net...
Yikes! I suspect a defect in the power supplies of the PC or the
printer
or
the wiring of the outlets they are plugged into.

I DO NOT THINK IT IS SAFE TO CONNECT THEM TOGETHER. Please don't.

I'm guessing they both have 3-wire power cords and are plugged into
different outlets, and one of the outlets is not grounded properly.
Is
that
the case?

Or the printer has a 2-wire power cord and has a defect in its power
supply.
Again, one of the outlets is probably not wired properly.

You can get a little tester with 3 neon lamps in it which you plug
into
an
outlet to check that the correct side is grounded. I urge you to do
so.

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:yAG0d.1311$yJ3.282@trndny08...
I felt a small shock when I touched the USB connector from the Canon
Pixma
IP1500 printer and the grounded PC case at the same time. It's not
a
60hz
AC type of shock but is felt as very brief pulses of approximately
2-3
pulses per second when printer is in off mode. These pulses are
faster
if
the printer is turned on. I put a neon tester between the USB cable
and
the
PC ground and it glew continuously but could not see the pulses on
the
neon
tester. Although the neon tester glew continuously, why did I only
feel
a
series of short pulses about 2-3 times per second. The shock feels
like
a
couple of milliamps through the finger.
Click to expand...
 
"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:I%I0d.204$W73.52@trndny03...
It's a brand new model of the printer that just came out last month.
Click to expand...
Any continuous potential, i.e., not static electricity, difference you can feel
with dry skin is definitely too much from a safety standpoint. Have you tried
measuring the voltage with a voltmeter?

In any case it's time to contact the printer manufacturer's help line and ask
them what they are going to do about replacing your defective printer or power
module before some one gets hurt using it.

--
James T. White
 
The USB cable sends periodic pulses to the PC even when off and this is what
is actually felt. It's not a standard 60hz shock like from a wall outlet
which would be much worse than a shock from the USB connection. Do you have
any USB printer and have you gotten the same shock from the USB connection?

"James T. White" <SPAMjtwhiteGUARD@SPAMhal-pcGUARD.org> wrote in message
news:4143a83e$0$448$a726171b@news.hal-pc.org...
"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:I%I0d.204$W73.52@trndny03...
It's a brand new model of the printer that just came out last month.


Any continuous potential, i.e., not static electricity, difference you can
feel
with dry skin is definitely too much from a safety standpoint. Have you
tried
measuring the voltage with a voltmeter?

In any case it's time to contact the printer manufacturer's help line and
ask
them what they are going to do about replacing your defective printer or
power
module before some one gets hurt using it.

--
James T. White
Click to expand...
 
The movement of the voltmeter isn't fast enough to measure short pulses.
The neon tester glew dimly when placed between USB connector and PC ground
but there isn't enough current to feel it except for the short pulses. The
neon tester goes out with even a very light touch between the USB connector
and the PC ground. The slight shock is felt only if I touch the USB
connector and PC case firmly, not if I touch it lightly. There isn't enough
current to cause a spark when connecting the USB connector to the PC.

"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in message
news:4143c829$1@mustang.speedfactory.net...
"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:xmO0d.565$VV2.219@trndny06...
The USB cable sends periodic pulses to the PC even when off and this is
what
is actually felt. It's not a standard 60hz shock like from a wall
outlet
which would be much worse than a shock from the USB connection. Do you
have
any USB printer and have you gotten the same shock from the USB
connection?

To feel a shock you need about 25 volts. Something seems to be wrong. My
next move would be to use a voltmeter to measure the pulses. I think
there's some kind of leakage in the power supply of either the printer or
the computer.
Click to expand...
 
Anything that will light a neon bulb is MORE than enough to destroy digital
circuits, and probably enough to endanger a human being.

Do you have an oscilloscope available?

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:KgR0d.237$W73.48@trndny03...
The movement of the voltmeter isn't fast enough to measure short pulses.
The neon tester glew dimly when placed between USB connector and PC ground
but there isn't enough current to feel it except for the short pulses.
The
neon tester goes out with even a very light touch between the USB
connector
and the PC ground. The slight shock is felt only if I touch the USB
connector and PC case firmly, not if I touch it lightly. There isn't
enough
current to cause a spark when connecting the USB connector to the PC.

"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in message
news:4143c829$1@mustang.speedfactory.net...

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:xmO0d.565$VV2.219@trndny06...
The USB cable sends periodic pulses to the PC even when off and this is
what
is actually felt. It's not a standard 60hz shock like from a wall
outlet
which would be much worse than a shock from the USB connection. Do you
have
any USB printer and have you gotten the same shock from the USB
connection?

To feel a shock you need about 25 volts. Something seems to be wrong.
My
next move would be to use a voltmeter to measure the pulses. I think
there's some kind of leakage in the power supply of either the printer or
the computer.
Click to expand...
 
It's not a linear power supply. It's a switch-mode power supply in a
rectangular box mounted to the bottom of the printer with a screw. The
label on the black box says AC adapter and has 120-220VAC input and a 24VDC
output.

"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:jTe1d.86129$C7.64538@amsnews05.chello.com...
"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:ryb1d.6770$sX2.4401@trndny09...
I don't have an oscilloscope available.
"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in message
news:4144c3a9$1@mustang.speedfactory.net...
Anything that will light a neon bulb is MORE than enough to destroy
digital
circuits, and probably enough to endanger a human being.

Do you have an oscilloscope available?

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:KgR0d.237$W73.48@trndny03...
The movement of the voltmeter isn't fast enough to measure short
pulses.
The neon tester glew dimly when placed between USB connector and PC
ground
but there isn't enough current to feel it except for the short
pulses.
The
neon tester goes out with even a very light touch between the USB
connector
and the PC ground. The slight shock is felt only if I touch the USB
connector and PC case firmly, not if I touch it lightly. There
isn't
enough
current to cause a spark when connecting the USB connector to the
PC.

"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
message
news:4143c829$1@mustang.speedfactory.net...

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:xmO0d.565$VV2.219@trndny06...
The USB cable sends periodic pulses to the PC even when off and
this
is
what
is actually felt. It's not a standard 60hz shock like from a
wall
outlet
which would be much worse than a shock from the USB connection.
Do
you
have
any USB printer and have you gotten the same shock from the USB
connection?

To feel a shock you need about 25 volts. Something seems to be
wrong.
My
next move would be to use a voltmeter to measure the pulses. I
think
there's some kind of leakage in the power supply of either the
printer
or
the computer.










Keith,

You need to kow:
- To feel a shock requires some tens of volts and some milli amperes of
current albeit for a very short time.
- To ignite a common neon bulb requires about 90V and it extinguishes
below
some 60V. Current in the micro ampere range.
- To measure voltages you need an electronic instrument with a high
resistance (>10MOhm). This is because you're dealing with high impedances
(otherwise you'd been dead already.) Check for AC *and* DC voltages.
- Equipment with a two pin mains connector are - or should be - "double
insulated". That's to say none of the metalic parts you can touch has a
galvanic connection with the mains or the ground. They're floating.

Assuming your mains installation is OK and following the discussion so far
the only thing I can imagine the cause of your shocking experiences is a
leaky power supply of the printer. That leak can be capacitive i.e. the
parasetic capacity of the transformer and/or a deliberately placed
capacitor
meant for decoupling. They are not necessarily defective but I can't see
that on this distance. It is also possible that these - or other
components
lost a part of their insulation resistance and became leaky.

It's hard to proceed without some electronic skills and equipment. You can
try another power supply or printer of the same type and look for
differences. I'd try an insulating transformer to do the same. A good one
is
shielded inside and has very low parasetic capacity to the mains. Even a
less professional one may solve your problem... if you can find one.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 6-9-2004
Click to expand...
 
I have many iron transformer based UL listed AC adapters and none of them
cause a shock to ground and they don't light the neon bulb either. The
capacitive leakage between primary to secondary is too small to be felt from
normal adapters. Do switch-mode adapters have higher leakage currents than
normal adapters? Normal adapters don't have any y capacitors between
primary and secondary unlike switch-mode ones. Y capacitors are used to
suppress EMI but are only found in SMPS.

"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:04L1d.14320$zh.7187@amsnews02.chello.com...
"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:juo1d.13904$z_3.10759@trndny07...
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:jTe1d.86129$C7.64538@amsnews05.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:ryb1d.6770$sX2.4401@trndny09...
I don't have an oscilloscope available.
"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
message
news:4144c3a9$1@mustang.speedfactory.net...
Anything that will light a neon bulb is MORE than enough to
destroy
digital
circuits, and probably enough to endanger a human being.

Do you have an oscilloscope available?

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:KgR0d.237$W73.48@trndny03...
The movement of the voltmeter isn't fast enough to measure short
pulses.
The neon tester glew dimly when placed between USB connector and
PC
ground
but there isn't enough current to feel it except for the short
pulses.
The
neon tester goes out with even a very light touch between the
USB
connector
and the PC ground. The slight shock is felt only if I touch the
USB
connector and PC case firmly, not if I touch it lightly. There
isn't
enough
current to cause a spark when connecting the USB connector to
the
PC.

"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
message
news:4143c829$1@mustang.speedfactory.net...

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:xmO0d.565$VV2.219@trndny06...
The USB cable sends periodic pulses to the PC even when off
and
this
is
what
is actually felt. It's not a standard 60hz shock like from a
wall
outlet
which would be much worse than a shock from the USB
connection.
Do
you
have
any USB printer and have you gotten the same shock from the
USB
connection?

To feel a shock you need about 25 volts. Something seems to be
wrong.
My
next move would be to use a voltmeter to measure the pulses. I
think
there's some kind of leakage in the power supply of either the
printer
or
the computer.










Keith,

You need to kow:
- To feel a shock requires some tens of volts and some milli amperes
of
current albeit for a very short time.
- To ignite a common neon bulb requires about 90V and it extinguishes
below
some 60V. Current in the micro ampere range.
- To measure voltages you need an electronic instrument with a high
resistance (>10MOhm). This is because you're dealing with high
impedances
(otherwise you'd been dead already.) Check for AC *and* DC voltages.
- Equipment with a two pin mains connector are - or should be -
"double
insulated". That's to say none of the metalic parts you can touch has
a
galvanic connection with the mains or the ground. They're floating.

Assuming your mains installation is OK and following the discussion so
far
the only thing I can imagine the cause of your shocking experiences is
a
leaky power supply of the printer. That leak can be capacitive i.e.
the
parasetic capacity of the transformer and/or a deliberately placed
capacitor
meant for decoupling. They are not necessarily defective but I can't
see
that on this distance. It is also possible that these - or other
components
lost a part of their insulation resistance and became leaky.

It's hard to proceed without some electronic skills and equipment. You
can
try another power supply or printer of the same type and look for
differences. I'd try an insulating transformer to do the same. A good
one
is
shielded inside and has very low parasetic capacity to the mains. Even
a
less professional one may solve your problem... if you can find one.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 6-9-2004


It's not a linear power supply. It's a switch-mode power supply in a
rectangular box mounted to the bottom of the printer with a screw. The
label on the black box says AC adapter and has 120-220VAC input and a
24VDC
output.


It nevertheless contains a transformer to separate the mains from the
printer. These type of power supplies use to run on >25kHz and needs much
smaller a transformer then the ones that run on 50/60Hz. The transformer
core is a ferrite instead of iron. But it is a transformer. There even may
be a second, much smaller, transformer used for the feedback although most
of the times a opto coupler is used for it these days.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 7-9-2004
Click to expand...
 
"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:l3S1d.4192$VV2.892@trndny06...
I have many iron transformer based UL listed AC adapters and none of them
cause a shock to ground and they don't light the neon bulb either.
Click to expand...
They should not. Nevertheless I met some supplies that did.

The
capacitive leakage between primary to secondary is too small to be felt
from
normal adapters.
Click to expand...
So if you do (feel it,) it may be defective or a bad design.

Do switch-mode adapters have higher leakage currents than
normal adapters?
Click to expand...
They should not.

Normal adapters don't have any y capacitors between
primary and secondary unlike switch-mode ones. Y capacitors are used to
suppress EMI but are only found in SMPS.
Click to expand...
They're the ones I was talking about and - again - may be defective or badly
designed.

petrus bitbyter

"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:04L1d.14320$zh.7187@amsnews02.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:juo1d.13904$z_3.10759@trndny07...
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:jTe1d.86129$C7.64538@amsnews05.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:ryb1d.6770$sX2.4401@trndny09...
I don't have an oscilloscope available.
"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
message
news:4144c3a9$1@mustang.speedfactory.net...
Anything that will light a neon bulb is MORE than enough to
destroy
digital
circuits, and probably enough to endanger a human being.

Do you have an oscilloscope available?

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:KgR0d.237$W73.48@trndny03...
The movement of the voltmeter isn't fast enough to measure
short
pulses.
The neon tester glew dimly when placed between USB connector
and
PC
ground
but there isn't enough current to feel it except for the short
pulses.
The
neon tester goes out with even a very light touch between the
USB
connector
and the PC ground. The slight shock is felt only if I touch
the
USB
connector and PC case firmly, not if I touch it lightly. There
isn't
enough
current to cause a spark when connecting the USB connector to
the
PC.

"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
message
news:4143c829$1@mustang.speedfactory.net...

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:xmO0d.565$VV2.219@trndny06...
The USB cable sends periodic pulses to the PC even when off
and
this
is
what
is actually felt. It's not a standard 60hz shock like from
a
wall
outlet
which would be much worse than a shock from the USB
connection.
Do
you
have
any USB printer and have you gotten the same shock from the
USB
connection?

To feel a shock you need about 25 volts. Something seems to
be
wrong.
My
next move would be to use a voltmeter to measure the pulses.
I
think
there's some kind of leakage in the power supply of either the
printer
or
the computer.










Keith,

You need to kow:
- To feel a shock requires some tens of volts and some milli amperes
of
current albeit for a very short time.
- To ignite a common neon bulb requires about 90V and it extinguishes
below
some 60V. Current in the micro ampere range.
- To measure voltages you need an electronic instrument with a high
resistance (>10MOhm). This is because you're dealing with high
impedances
(otherwise you'd been dead already.) Check for AC *and* DC voltages.
- Equipment with a two pin mains connector are - or should be -
"double
insulated". That's to say none of the metalic parts you can touch has
a
galvanic connection with the mains or the ground. They're floating.

Assuming your mains installation is OK and following the discussion
so
far
the only thing I can imagine the cause of your shocking experiences
is
a
leaky power supply of the printer. That leak can be capacitive i.e.
the
parasetic capacity of the transformer and/or a deliberately placed
capacitor
meant for decoupling. They are not necessarily defective but I can't
see
that on this distance. It is also possible that these - or other
components
lost a part of their insulation resistance and became leaky.

It's hard to proceed without some electronic skills and equipment.
You
can
try another power supply or printer of the same type and look for
differences. I'd try an insulating transformer to do the same. A good
one
is
shielded inside and has very low parasetic capacity to the mains.
Even
a
less professional one may solve your problem... if you can find one.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
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It's not a linear power supply. It's a switch-mode power supply in a
rectangular box mounted to the bottom of the printer with a screw. The
label on the black box says AC adapter and has 120-220VAC input and a
24VDC
output.


It nevertheless contains a transformer to separate the mains from the
printer. These type of power supplies use to run on >25kHz and needs
much
smaller a transformer then the ones that run on 50/60Hz. The transformer
core is a ferrite instead of iron. But it is a transformer. There even
may
be a second, much smaller, transformer used for the feedback although
most
of the times a opto coupler is used for it these days.

petrus bitbyter



---
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Click to expand...

---
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Well, that's a great warning. I could have said that myself. You also could
as you found it out the hard way.

Wonder whether this printer(s power supply) meets the local (and/or
national) safety regulations.

The 10mA they mentioned looks very strange to me. Can't imagine they're
right. I have my doubts about the technical skills of that consumer
relations department personal. Most of the time they repair clients and
never printers.

petrus bitbyter


"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:6Y12d.19382$z_3.18711@trndny07...
I have contacted Canon tech support and they transferred me to consumer
relations department and they said there is current going through the USB
cable and I asked how much current and they said up to 10 milliamps.
Canon
just gave a warning over the phone to be careful never to touch the metal
part of the USB cable and any grounded objects at the same time.

"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:nUU1d.14850$zh.3816@amsnews02.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:l3S1d.4192$VV2.892@trndny06...
I have many iron transformer based UL listed AC adapters and none of
them
cause a shock to ground and they don't light the neon bulb either.

They should not. Nevertheless I met some supplies that did.

The
capacitive leakage between primary to secondary is too small to be felt
from
normal adapters.

So if you do (feel it,) it may be defective or a bad design.

Do switch-mode adapters have higher leakage currents than
normal adapters?

They should not.

Normal adapters don't have any y capacitors between
primary and secondary unlike switch-mode ones. Y capacitors are used
to
suppress EMI but are only found in SMPS.

They're the ones I was talking about and - again - may be defective or
badly
designed.

petrus bitbyter


"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:04L1d.14320$zh.7187@amsnews02.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:juo1d.13904$z_3.10759@trndny07...
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:jTe1d.86129$C7.64538@amsnews05.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:ryb1d.6770$sX2.4401@trndny09...
I don't have an oscilloscope available.
"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
message
news:4144c3a9$1@mustang.speedfactory.net...
Anything that will light a neon bulb is MORE than enough to
destroy
digital
circuits, and probably enough to endanger a human being.

Do you have an oscilloscope available?

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:KgR0d.237$W73.48@trndny03...
The movement of the voltmeter isn't fast enough to measure
short
pulses.
The neon tester glew dimly when placed between USB connector
and
PC
ground
but there isn't enough current to feel it except for the
short
pulses.
The
neon tester goes out with even a very light touch between
the
USB
connector
and the PC ground. The slight shock is felt only if I touch
the
USB
connector and PC case firmly, not if I touch it lightly.
There
isn't
enough
current to cause a spark when connecting the USB connector
to
the
PC.

"Michael A. Covington" <look@ai.uga.edu.for.address> wrote
in
message
news:4143c829$1@mustang.speedfactory.net...

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in
message
news:xmO0d.565$VV2.219@trndny06...
The USB cable sends periodic pulses to the PC even when
off
and
this
is
what
is actually felt. It's not a standard 60hz shock like
from
a
wall
outlet
which would be much worse than a shock from the USB
connection.
Do
you
have
any USB printer and have you gotten the same shock from
the
USB
connection?

To feel a shock you need about 25 volts. Something seems
to
be
wrong.
My
next move would be to use a voltmeter to measure the
pulses.
I
think
there's some kind of leakage in the power supply of either
the
printer
or
the computer.










Keith,

You need to kow:
- To feel a shock requires some tens of volts and some milli
amperes
of
current albeit for a very short time.
- To ignite a common neon bulb requires about 90V and it
extinguishes
below
some 60V. Current in the micro ampere range.
- To measure voltages you need an electronic instrument with a
high
resistance (>10MOhm). This is because you're dealing with high
impedances
(otherwise you'd been dead already.) Check for AC *and* DC
voltages.
- Equipment with a two pin mains connector are - or should be -
"double
insulated". That's to say none of the metalic parts you can touch
has
a
galvanic connection with the mains or the ground. They're
floating.

Assuming your mains installation is OK and following the
discussion
so
far
the only thing I can imagine the cause of your shocking
experiences
is
a
leaky power supply of the printer. That leak can be capacitive
i.e.
the
parasetic capacity of the transformer and/or a deliberately placed
capacitor
meant for decoupling. They are not necessarily defective but I
can't
see
that on this distance. It is also possible that these - or other
components
lost a part of their insulation resistance and became leaky.

It's hard to proceed without some electronic skills and equipment.
You
can
try another power supply or printer of the same type and look for
differences. I'd try an insulating transformer to do the same. A
good
one
is
shielded inside and has very low parasetic capacity to the mains.
Even
a
less professional one may solve your problem... if you can find
one.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 6-9-2004


It's not a linear power supply. It's a switch-mode power supply
in
a
rectangular box mounted to the bottom of the printer with a screw.
The
label on the black box says AC adapter and has 120-220VAC input and
a
24VDC
output.


It nevertheless contains a transformer to separate the mains from the
printer. These type of power supplies use to run on >25kHz and needs
much
smaller a transformer then the ones that run on 50/60Hz. The
transformer
core is a ferrite instead of iron. But it is a transformer. There even
may
be a second, much smaller, transformer used for the feedback although
most
of the times a opto coupler is used for it these days.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 7-9-2004





---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 6-9-2004
Click to expand...

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 7-9-2004
 
There is even a slight buzzing sensation when rubbing a finger across the
USB connection with just a very light touch and it goes away when the
printer is unplugged. Have you had this happen with your printer?

"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:is32d.95835$C7.12587@amsnews05.chello.com...
Well, that's a great warning. I could have said that myself. You also
could
as you found it out the hard way.

Wonder whether this printer(s power supply) meets the local (and/or
national) safety regulations.

The 10mA they mentioned looks very strange to me. Can't imagine they're
right. I have my doubts about the technical skills of that consumer
relations department personal. Most of the time they repair clients and
never printers.

petrus bitbyter


"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:6Y12d.19382$z_3.18711@trndny07...
I have contacted Canon tech support and they transferred me to consumer
relations department and they said there is current going through the
USB
cable and I asked how much current and they said up to 10 milliamps.
Canon
just gave a warning over the phone to be careful never to touch the
metal
part of the USB cable and any grounded objects at the same time.

"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:nUU1d.14850$zh.3816@amsnews02.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:l3S1d.4192$VV2.892@trndny06...
I have many iron transformer based UL listed AC adapters and none of
them
cause a shock to ground and they don't light the neon bulb either.

They should not. Nevertheless I met some supplies that did.

The
capacitive leakage between primary to secondary is too small to be
felt
from
normal adapters.

So if you do (feel it,) it may be defective or a bad design.

Do switch-mode adapters have higher leakage currents than
normal adapters?

They should not.

Normal adapters don't have any y capacitors between
primary and secondary unlike switch-mode ones. Y capacitors are used
to
suppress EMI but are only found in SMPS.

They're the ones I was talking about and - again - may be defective or
badly
designed.

petrus bitbyter


"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:04L1d.14320$zh.7187@amsnews02.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:juo1d.13904$z_3.10759@trndny07...
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in
message
news:jTe1d.86129$C7.64538@amsnews05.chello.com...

"Keith Weisshar" <keith.weisshar@verizon.net> schreef in bericht
news:ryb1d.6770$sX2.4401@trndny09...
I don't have an oscilloscope available.
"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
message
news:4144c3a9$1@mustang.speedfactory.net...
Anything that will light a neon bulb is MORE than enough to
destroy
digital
circuits, and probably enough to endanger a human being.

Do you have an oscilloscope available?

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in
message
news:KgR0d.237$W73.48@trndny03...
The movement of the voltmeter isn't fast enough to measure
short
pulses.
The neon tester glew dimly when placed between USB
connector
and
PC
ground
but there isn't enough current to feel it except for the
short
pulses.
The
neon tester goes out with even a very light touch between
the
USB
connector
and the PC ground. The slight shock is felt only if I
touch
the
USB
connector and PC case firmly, not if I touch it lightly.
There
isn't
enough
current to cause a spark when connecting the USB connector
to
the
PC.

"Michael A. Covington" <look@ai.uga.edu.for.address> wrote
in
message
news:4143c829$1@mustang.speedfactory.net...

"Keith Weisshar" <keith.weisshar@verizon.net> wrote in
message
news:xmO0d.565$VV2.219@trndny06...
The USB cable sends periodic pulses to the PC even when
off
and
this
is
what
is actually felt. It's not a standard 60hz shock like
from
a
wall
outlet
which would be much worse than a shock from the USB
connection.
Do
you
have
any USB printer and have you gotten the same shock from
the
USB
connection?

To feel a shock you need about 25 volts. Something seems
to
be
wrong.
My
next move would be to use a voltmeter to measure the
pulses.
I
think
there's some kind of leakage in the power supply of
either
the
printer
or
the computer.










Keith,

You need to kow:
- To feel a shock requires some tens of volts and some milli
amperes
of
current albeit for a very short time.
- To ignite a common neon bulb requires about 90V and it
extinguishes
below
some 60V. Current in the micro ampere range.
- To measure voltages you need an electronic instrument with a
high
resistance (>10MOhm). This is because you're dealing with high
impedances
(otherwise you'd been dead already.) Check for AC *and* DC
voltages.
- Equipment with a two pin mains connector are - or should be -
"double
insulated". That's to say none of the metalic parts you can
touch
has
a
galvanic connection with the mains or the ground. They're
floating.

Assuming your mains installation is OK and following the
discussion
so
far
the only thing I can imagine the cause of your shocking
experiences
is
a
leaky power supply of the printer. That leak can be capacitive
i.e.
the
parasetic capacity of the transformer and/or a deliberately
placed
capacitor
meant for decoupling. They are not necessarily defective but I
can't
see
that on this distance. It is also possible that these - or other
components
lost a part of their insulation resistance and became leaky.

It's hard to proceed without some electronic skills and
equipment.
You
can
try another power supply or printer of the same type and look
for
differences. I'd try an insulating transformer to do the same. A
good
one
is
shielded inside and has very low parasetic capacity to the
mains.
Even
a
less professional one may solve your problem... if you can find
one.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 6-9-2004


It's not a linear power supply. It's a switch-mode power supply
in
a
rectangular box mounted to the bottom of the printer with a screw.
The
label on the black box says AC adapter and has 120-220VAC input
and
a
24VDC
output.


It nevertheless contains a transformer to separate the mains from
the
printer. These type of power supplies use to run on >25kHz and
needs
much
smaller a transformer then the ones that run on 50/60Hz. The
transformer
core is a ferrite instead of iron. But it is a transformer. There
even
may
be a second, much smaller, transformer used for the feedback
although
most
of the times a opto coupler is used for it these days.

petrus bitbyter



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 7-9-2004





---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 6-9-2004





---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.754 / Virus Database: 504 - Release Date: 7-9-2004
Click to expand...
 
Keith Weisshar <keith.weisshar@verizon.net> wrote:
: There is even a slight buzzing sensation when rubbing a finger across the
: USB connection with just a very light touch and it goes away when the
: printer is unplugged. Have you had this happen with your printer?

: "petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
....
: > >> >> > > > > >> > is actually felt. It's not a standard 60hz shock like

Congratulation to Keith:

Top quoting 300 line up 9 levels deep to add some few lines....

Argh!

--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
 
"Keith Weisshar" <keith.weisshar@verizon.net> wrote in message
news:k5y2d.14013$W73.5795@trndny03...
There is even a slight buzzing sensation when rubbing a finger across the
USB connection with just a very light touch and it goes away when the
printer is unplugged. Have you had this happen with your printer?
Click to expand...
This absolutely should not happen. There's not much difference between a
shock you can feel and a shock that can kill you. Either the power supply
is defective or the outlet that it's plugged into is miswired. (Probably
the former.)

We should no longer be discussing whether it is normal or safe. IT IS NOT.
We should be getting it fixed.

What I'm guessing is that in the printer power supply, there is leakage from
120V AC to ground, through a high enough resistance that all of the leakage
gets absorbed by the (correctly functioning) ground connection of the
computer when the two are connected together. There are also other
possibilities.

When Tech Support mentioned 10 mA they were probably talking about the
ability of USB ports to supply 5-volt power to other devices... completely
irrelevant.
 
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