Tingles from DVD players

[Russ_Verdon]

Hi, I just did a round of "kerbside shopping" and picked up 2x Digitor DVD
players from the same place. They both work. The only thing I can think is
that they give you a small shock between their chassis and power earth. I
can only surmise that the owner thought they were faulty and ditched them as
a result. I have picked up another DVD player in similar circunstances,
going, but tingling.
I believe the shock would be some capacitive coupling to their chassis from
the switchmode PS. I can measure 105 volts AC from their chassis to earth,
but no current .
Is there any rule that stops you earthing these devices, given that the
connection via the signal leads to an earthed amp etc would probably do this
anyway?
Do the manufacturers expect all devices to be turned off so that customers
don't experience shocks when changing leads around? If chassis earthing
elminates this issue, then it would be a nice feature and customer friendly
to do so. I guess the amount of copper / star washer etc saved per unit for
them outweighs thoughts for the customer.
Any comments?

Russell

 

[Phil Allison]

"Russ_Verdon"

Hi, I just did a round of "kerbside shopping" and picked up 2x Digitor
DVD
players from the same place. They both work. The only thing I can think is
that they give you a small shock between their chassis and power earth. I
can only surmise that the owner thought they were faulty and ditched them
as
a result. I have picked up another DVD player in similar circunstances,
going, but tingling.
I believe the shock would be some capacitive coupling to their chassis
from
the switchmode PS. I can measure 105 volts AC from their chassis to earth,
but no current .
Is there any rule that stops you earthing these devices, given that the
connection via the signal leads to an earthed amp etc would probably do
this
anyway?

** Yes - the units are not longer "double insulated" or of "class 2"
construction if you substitute a 3 core lead.

Do the manufacturers expect all devices to be turned off so that customers
don't experience shocks when changing leads around?

** Only a few folk feel any tingle at all.

If chassis earthing
elminates this issue, then it would be a nice feature and customer
friendly
to do so.

** Completely silly.

The use of Class 2 construction is a VERY deliberate decision and for very
good reasons.

I guess the amount of copper / star washer etc saved per unit for
them outweighs thoughts for the customer.

** Absolute crapology.

Any comments?

** You seriously temp me.

Never heard of earth loop hum ?????




.......... Phil

 

[Chris Jones]

Phil Allison wrote:

"Russ_Verdon"

Hi, I just did a round of "kerbside shopping" and picked up 2x Digitor
DVD
players from the same place. They both work. The only thing I can think
is that they give you a small shock between their chassis and power
earth. I can only surmise that the owner thought they were faulty and
ditched them as
a result. I have picked up another DVD player in similar circunstances,
going, but tingling.
I believe the shock would be some capacitive coupling to their chassis
from
the switchmode PS. I can measure 105 volts AC from their chassis to
earth, but no current .
Is there any rule that stops you earthing these devices, given that the
connection via the signal leads to an earthed amp etc would probably do
this
anyway?


** Yes - the units are not longer "double insulated" or of "class 2"
construction if you substitute a 3 core lead.

Sure, that seems obvious. The device would then be modified, the original
electrical approval would not be valid, and it would not be possible to
approve the device as a class 2 device with the case earthed. Are you
aware of any technical reason why the device could not be approved as a
class 1 device (hypothetically, since the cost of testing would be more
than prohibitive)? To the best of my knowledge the insulation requirements
of a class 2 device are more strict than would be required for a class 1
device, though I don't know if there are any fusing requirements for class
1 which would not have applied to the class 2 device when it was built.

Do the manufacturers expect all devices to be turned off so that
customers don't experience shocks when changing leads around?


** Only a few folk feel any tingle at all.


If chassis earthing
elminates this issue, then it would be a nice feature and customer
friendly
to do so.


** Completely silly.

The use of Class 2 construction is a VERY deliberate decision and for very
good reasons.

Apart from the earth loop hum you refer to, what reasons are you referring
to?

I guess the amount of copper / star washer etc saved per unit for
them outweighs thoughts for the customer.


** Absolute crapology.

Any comments?


** You seriously temp me.

Never heard of earth loop hum ?????




......... Phil

Chris

 

[Phil Allison]

"Chris Jones"

Phil Allison wrote:

Is there any rule that stops you earthing these devices, given that the
connection via the signal leads to an earthed amp etc would probably do
this
anyway?


** Yes - the units are not longer "double insulated" or of "class 2"
construction if you substitute a 3 core lead.

Sure, that seems obvious.

** You have completely missed the point.

The device would then be modified, the original
electrical approval would not be valid,

** Correct - so the markings on the unit (ie "class 2" and the double
square symbols) would be then ILLEGAL.

and it would not be possible to
approve the device as a class 2 device with the case earthed. Are you
aware of any technical reason why the device could not be approved as a
class 1 device (hypothetically, since the cost of testing would be more
than prohibitive)?

** Yawn.

This is an entirely separate issue to the OP's question AND my reply.

If chassis earthing elminates this issue, then it would be a nice
feature and customer friendly to do so.


** Completely silly.

The use of Class 2 construction is a VERY deliberate decision and for
very
good reasons.

Apart from the earth loop hum you refer to, what reasons are you referring
to?

** 1. Class 2 construction is far SAFER for the user.

2. Class 2 construction meets world wide electrical approvals making it far
easier for makers to market the same design world wide.

3. The use of class 2 is almost universal for some classes of electronic
equipment.

4. There is a PROHIBITION on interconnecting class 1 and class 2 equipment.





......... Phil

 

[Jasen Betts]

On 2006-03-19, Phil Allison <philallison@tpg.com.au> wrote:

** Completely silly.

The use of Class 2 construction is a VERY deliberate decision and for
very
good reasons.

Apart from the earth loop hum you refer to, what reasons are you referring
to?

** 1. Class 2 construction is far SAFER for the user.

2. Class 2 construction meets world wide electrical approvals making it far
easier for makers to market the same design world wide.

3. The use of class 2 is almost universal for some classes of electronic
equipment.

4. There is a PROHIBITION on interconnecting class 1 and class 2 equipment.

like a laplink cable?

Bye.
Jasen

 

[Phil Allison]

"Chris Jones"



** Do you constantly move the goalposts at sporting events too ?





........... Phil

 

[Phil Allison]

"Terry Given"

a major advantage of class 2 is that its cheaper.

** Bullshit it is.

The specs for the AC supply transformer alone are way beyond that for class
1.

The design rules for every part of the AC side are way tougher.

the plug, cable and interconnects cost less,

** By a few cents only.

and because of the double insulation, none of the metalwork has to be
earthed, which it does with class 1 - for many standards the metalwork
earthing must carry the rated current, further increasing the cost.

** What absolute drivel.

The above scenario can only happen when people fiddle with things,

** More " Pinball Wizard " bullshit.

so is not relevant to manufacturers (they build them right).

** It is *very elevata" to the increased safety of class 2.

It is *very relevant" to the PROHIBITION on earthing a class 2 appliance.

Such a scenario also occurs with a single class 1 appliance wired up by
the same dickhead.

** But NOT a system of interconnected class 1 appliances.

Hence the prohibition on earthing a class 2 appliance or system thereof.

They are very safe until you do that.

Voila, live chassis (and dead operator).

** Please go try it now.




........ Phil

 

[Phil Allison]

"The Pinball Wizard of Nelson "

a major advantage of class 2 is that its cheaper.


** Bullshit it is.

The specs for the AC supply transformer alone are way beyond that for
class 1.

double insulation pretty much means 2 sets of insulation,

** Absolute bullshit.

so that when one fails there is still one left.

** Absolute bullshit.

yes the xfmr is a bit more expensive,

** Much more - the cheapest construction methods are outlawed.

The popular and cheap toroidal is basically outlawed.

but a whole bunch of other stuff gets cheaper.

** Absolute bullshit.

look inside a hair

** The subject is DVD players and the like - fuckhead.

The design rules for every part of the AC side are way tougher.


not really,

** Get stuffed - Kiwi LIAR !!




........ Phil

 

[Phil Allison]

"The Pinball Wizard of Nelson "

a major advantage of class 2 is that its cheaper.


** Bullshit it is.

The specs for the AC supply transformer alone are way beyond that for
class 1.

double insulation pretty much means 2 sets of insulation,


** Absolute bullshit.


so that when one fails there is still one left.



** Absolute bullshit.


ROTFLMAO!

** Go fuck yourself - you useless Kiwi ARSEHOLE .

first, lets un-snip what I posted:

"double insulation pretty much means 2 sets of insulation, so that when
one fails there is still one left"

** No.

The term "double insulation" is the popular name for "class 2" construction
= a whole set of technical design rules and restricted materials approvals
that make it * SAFE * to use and sell an appliance that has no connection
to the supply earth as a means of preventing electric shock hazard to users.

All way over this Kiwi fuckwit's pointy head.

In other words, exactly what I said.

** Wrong context - Kiwi ARSEHOLE.

yes the xfmr is a bit more expensive,

** Much more - the cheapest construction methods are outlawed.

pah. look at those sorts of xfmrs, its not very complex.

** Learn to read - you dumb Kiwi ARSEHOLE.

The popular and cheap toroidal is basically outlawed.


on what basis?

** Go read AS3108 some day - ARSEHOLE.

Then figure why toroidals are extremely rare in class 2 gear, consumer or
otherwise.




........ Phil

 

[David, not to be confused]

I might as well add my $0.02 worth here too.

"Russ_Verdon" <verdonsATtpgi.com.au> wrote in message
news:441d2338@dnews.tpgi.com.au...

Hi, I just did a round of "kerbside shopping" and picked up 2x Digitor DVD
players from the same place. They both work. The only thing I can think is
that they give you a small shock between their chassis and power earth. I
can only surmise that the owner thought they were faulty and ditched them as
a result. I have picked up another DVD player in similar circunstances,
going, but tingling.

This is a well known and allowed for condition in safety standards. It is
referred
to as "touch current" and was previosuly referred to as leakage current. The
safe
limit for touch current in Class 2 devices is 0.25 mA and this lies within the
perception range for some people. Touch current is likely due to the current
passing
through small value capacitors connected between the chassis and the primary
power circuits. This is usually for ESD (electro-static discharge)
compatibility in
the case of audio/video equipment.

Is there any rule that stops you earthing these devices, given that the
connection via the signal leads to an earthed amp etc would probably
do this anyway?

There is no rule in the safety or wiring standards that prevents you from
doing so, but introducing an earth is not a good idea since it may cause
unintended earth loop currents to flow through other circuits. This can lead
to humm and noise, etc.

Do the manufacturers expect all devices to be turned off so that customers
don't experience shocks when changing leads around? If chassis earthing
elminates this issue, then it would be a nice feature and customer friendly
to do so. I guess the amount of copper / star washer etc saved per unit for
them outweighs thoughts for the customer.
Any comments?

Russell

Among other reasons, it also has to do with cost, but not as you might imagine.
By floating the chassis there is no need to use audio baluns or isolating
transformers in the input and output interconnection stages to remove
extraneous circulating supply currents or to provide electrical safety.

I read some of the other replies and would also like to add the following.

1. There is no prohibition on interconection of Class 1 and Class 2 equipment.
The only safety related condition is that any earthing required for safety of
the
Class 1 device is maintained at the desired level. Which is 1.6 times the
rated
current of an inherent protective device (eg. internal fusing).

2. Equipment that was marked "Do Not Earth" was often done so because the
internal circuitry was "live" and separated from accessible conductive parts by
double/reinforced insulation. Earthing the internal circuitry would be
potentially
hazardous in this case.

More commonly the "do not earth" instruction is for when the equipment is
supplied to countries that do not have the MEN (TNC-S) mains supply wiring
scheme. In those countries there is a separate earthing terminal or bonding
point
on the equipment chassis, and more often than not, no mains plug is supplied on
the cord. Equipment that is to be earthed has a plug added, and the chassis
bonded to
earth at the time of installation. For floating chassis devices the do not
earth instruction
is to specifically draw attention to not to bond to earth.

3. For small A/V and ITE, making Class 2 equipment costs almost the same as
Class 1
equipment. Class 1 is of benefit in high power appliances like toasters,
ovens, etc.

4. Class 2 construction does not mean double insulation. Double insulation
may be a
type of Class 2 construction but reinforced insulation is now more common.

5. Someone mentioned triple insulated wire is not common. It is now very
common,
being the preferred method to construct very small footprint concentric wound
transformers in smal SMPSUs. The majority of mobile phone power supplies I
have examined (say, since 2000) use triple insulated wire as the secondary
winding.
This way the static screen and the primary can be conductively coupled, doing
away
with the additional layers of insulation that would otherwise be needed.

Most of the above can be found in AS/NZS 60065 and/or AS/NZS 60950-1

 

[Phil Allison]

"David, not to be confused with the other Davids."

Is there any rule that stops you earthing these devices, given that the
connection via the signal leads to an earthed amp etc would probably
do this anyway?

There is no rule in the safety or wiring standards that prevents you from
doing so,

** Of course there is !!

A Class 2 appliance must not be earthed or it ceases to be one.

I read some of the other replies and would also like to add the following.

1. There is no prohibition on interconection of Class 1 and Class 2
equipment.

** There is.

A Class 2 appliance must not be earthed.

The only safety related condition is that any earthing required for safety
of
the Class 1 device is maintained at the desired level. Which is 1.6 times
the
rated current of an inherent protective device (eg. internal fusing).

** You are just making this crazy drivel up.

The earthing requirements for a class 1 appliance relate to the copper cross
section of the earth wire used, ie must not be not less than 1 sq mm. (
AS3100)

2. Equipment that was marked "Do Not Earth" was often done so because the
internal circuitry was "live" and separated from accessible conductive
parts by
double/reinforced insulation. Earthing the internal circuitry would be
potentially hazardous in this case.

** Plenty of class 2 items are labelled "Do Not Earth" where no such thing
existed.

( snip more irrelevant drivel )

4. Class 2 construction does not mean double insulation.

** Correct - but the names have become synonyms as far as categorising an
appliance is concerned.




........ Phil

 

[Phil Allison]

"Terry Given"

the prohibition on earthing class 2 appliances does not relate to
consumers plugging them into class 1 appliances,

** Yawn .......

A safety risk is created by so doing - possibly a very serious one.




........ Phil

 

[David, not to be confused]

are you aware of any triple-insulated foils?

I haven't seen any (yet) that aren't of wrapped and folded insulation lay-up.

The mandrel test for flexibility and adherence would pretty much exclude the
use of other than round cross-sections in order to pass the 6 kV dielectric
strength test (based on my experience to date, the edge of the foil would
damage the layer(s) of extruded or spiral wrpped insulation).

Now I have said this, I will probably see one tomorrow

High current devices using foil windings usually have very bulky concentric
windings, since the insulation layup for each layer is sometimes as thick or
thicker than the foil. Must be a right bugger to make them to even
semi-precise tolerances.

 

[Jasen Betts]

On 2006-03-23, Phil Allison <philallison@tpg.com.au> wrote:

"David, not to be confused with the other Davids."

Is there any rule that stops you earthing these devices, given that the
connection via the signal leads to an earthed amp etc would probably
do this anyway?

There is no rule in the safety or wiring standards that prevents you from
doing so,


** Of course there is !!

A Class 2 appliance must not be earthed or it ceases to be one.

And that would be a problem how?

I read some of the other replies and would also like to add the following.

1. There is no prohibition on interconection of Class 1 and Class 2
equipment.

** There is.

A Class 2 appliance must not be earthed.

says you...

what's the deal with laplink cables ?

and connecting what's that bad thing that going to happen by connecting my
VCR and DVD player to my ancient TV (Phillips K9ii) which has an eathed
antenna connector. and my junk CD player (CD-rom drive in an old apple
external 5.25" enclosure with RCA sockets on the back) (earthed) is connected
to my cheap sterio.

--

Bye.
Jasen

 

[Phil Allison]

"Alan Rutlidge" = The Rutmaniac Arse Bandit

See: http://www.advantra.net/contact_us.htm


The Rutmaniac Arse Bandit has **NEVER** told us how much money
that Thai pal he " imported " into Perth ripped off from his credit card
and bank accounts.

He has refused, over and over, to say why he never reported the crime his
Thai boy lover committed to his Bank or to the WA police.


** This post of his on " rec.travel asia " from Oct 11, 1997 explains the
event:

------------------------------­------------------------------­---


" WARNING - Tourism dangers for Gay Tourists in Thailand



In my case I was coerced into sponsoring a Thai into Australia. I was
lead down the garden path into a false sense of security about my
relationship with this person. His aim was clearly to get me to purswade
the Australian Embassy to grant him a visa. Once here I didn't exist after
he drained my bank account and ran my credit card into overdraft.


Alan Rutlidge (Perth Western Australia) "


----------------------------- ------------------------------------


** The 1997 date pretty much co-incidences with the enactment of
Section 50 BA of the Commonwealth Crimes Act.

This is the law that finally made engaging in or promoting under age
sex tourism a criminal offence - max penalty 17 years in jail.


BTW

The legal age of consent for gay males in WA in 1997 was 21 years old.


Come on - Arse Bandit - we all need to know if you were being
blackmailed.

BTW

I do not care how many of your vile, criminal colleagues you organise
to intimidate me.

It only makes you look so very much WORSE !!!



......... Phil

 

[Phil Allison]

<mdhjwh@iprimus.com.au>


** Beware !!!!

The above halfwit is a female impersonator from northern Tasmania

Goes by the handle "Ayn Marx ".

Might as well be Groucho Marx !!!

If anyone wants to avoid all the agro here you're welcome over on Oz
Hi-Fi & HT :-

** ROTFL !!

A very recently set up chat room for fuckwit audiophools, moderated by
control freaks & psychopaths !!

Go for it dudes ......




........ Phil

 

[Phil Allison]

<mdhjwh@iprimus.com.au>


** Beware !!!!

The above halfwit is a female impersonator from northern Tasmania

Goes by the handle "Ayn Marx ".

Might as well be Groucho Marx !!!

If anyone wants to avoid all the agro here you're welcome over on Oz
Hi-Fi & HT :-

** ROTFL !!

A very recently set up chat room for fuckwit audiophools, moderated by
control freaks & psychopaths !!

Go for it dudes ......




........ Phil

 

If anyone wants to avoid all the agro here you're welcome over on Oz
Hi-Fi & HT :-
http://forum.aushifi.com/
.........a moderated forum that allows the posting of graphics,
circuit
diagrams etc and avoids that flame wars that are destroying so many
newsgroups.

 

If anyone wants to avoid all the agro here you're welcome over on Oz
Hi-Fi & HT :-
http://forum.aushifi.com/
........................a moderated forum that allows the posting of
graphics, circuit
diagrams etc and avoids that flame wars that are destroying so many
newsgroups.

 

[Phil Allison]

<mdhjwh@iprimus.com.au>


** Beware !!!!

The above halfwit is a female impersonator from northern Tasmania

Goes by the handle "Ayn Marx ".

Might as well be Groucho Marx !!!

If anyone wants to avoid all the agro here you're welcome over on Oz
Hi-Fi & HT :-

** ROTFL !!

A very recently set up chat room for fuckwit audiophools, moderated by
control freaks & psychopaths !!

Go for it dudes ......




........ Phil