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Tingles from DVD players

Discussion in 'Hobby Electronics' started by Russ_Verdon, Mar 19, 2006.

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  1. Russ_Verdon

    Russ_Verdon Guest

    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
     
  2. Phil Allison

    Phil Allison Guest

    "Russ_Verdon"

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


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


    ** Completely silly.

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


    ** Absolute crapology.

    ** You seriously temp me.

    Never heard of earth loop hum ?????




    .......... Phil
     
  3. Phil Allison

    Phil Allison Guest

    "Chris Jones"

    ** You have completely missed the point.


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


    ** Yawn.

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



    ** 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
     
  4. Phil Allison

    Phil Allison Guest



    ** Piss off - kiwi tenth wit.

    The sheep are missing you.





    ........ Phil
     
  5. Phil Allison

    Phil Allison Guest

    "Chris Jones"



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





    ........... Phil
     
  6. Phil Allison

    Phil Allison Guest

    "Chris Jones"

    ** Have you never seen the words " Double Insulated - Do Not Earth " on
    the back of a class 2 item ??

    Pretty clear isn't it?


    ** It is not prohibited by criminal law - so no police officer will arrest
    you for doing it.

    But it is an * unsafe practice* that could be considered as " serious
    negligence " by a court if a person were injured or killed.


    ** " Double Insulated - Do Not Earth " on the back of the player is a
    *stronger warning* that anything printed in a user manual that likely gets
    lost with the packaging.

    Equipment makers are not liable for what users may WRONGLY do when
    interconnecting items of gear - so just ignore the issue.

    The matter is very much an *X rated topic * in the home entertainment
    electronics industry.


    ** Imagine a hi-fi system with every item in it class 2 - so there is no AC
    ground to the metalwork.

    Next, an item is added to the system, ie a nice old valve tuner just bought
    from Ebay but with no AC plug.

    Next, the user inadvertently wires up the new plug wrongly with active and
    earth reversed and makes all the connections.

    The hi-fi system will still work just as before ( but not the tuner) but
    with ALL the metalwork, connecting leads and even the loud speakers now
    LIVE !!!

    In countries with 240 volt AC power, this is a FATAL accident scenario
    !!!!


    NOTE:

    One of the BIGGEST user safety advantages of class 2 construction is that
    no matter how WRONGLY the AC plug is wired & no matter what is wrong with
    the AC outlet, you cannot get active onto the earth of the gear.




    ......... Phil
     
  7. Phil Allison

    Phil Allison Guest

    "Terry Given"

    ** 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.


    ** By a few cents only.


    ** What absolute drivel.


    ** More " Pinball Wizard " bullshit.


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

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



    ** 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.



    ** Please go try it now.




    ........ Phil
     
  8. Phil Allison

    Phil Allison Guest

    "The Pinball Wizard of Nelson "


    ** Absolute bullshit.


    ** Absolute bullshit.


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

    The popular and cheap toroidal is basically outlawed.



    ** Absolute bullshit.


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


    ** Get stuffed - Kiwi LIAR !!




    ........ Phil
     
  9. Phil Allison

    Phil Allison Guest

    "The Pinball Wizard of Nelson "


    ** Go **** yourself - you useless Kiwi ARSEHOLE .



    ** 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.



    ** Wrong context - Kiwi ARSEHOLE.



    ** Learn to read - you dumb Kiwi ARSEHOLE.



    ** Go read AS3108 some day - ARSEHOLE.

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




    ........ Phil
     
  10. I've just checked all the double insulated items in my home and NONE
    of them carry a warning such as you describe. It would be useful to
    know how general such a warning is. I suggest everyone reading this
    thread check their equipment and report back their findings. My
    equipment includes items from NEC, Philips, Sony, Teac, Mitsubishi,
    Sanyo & Microsoft.

    snip
    So where does the "PROHIBITION" come from?
    Previously you said such interconnection was prohibited, now you're
    saying to ignore the issue??
    If this danger was significant then the use of Class 2 equipment is
    inherently unsafe because it would be relying on user action to make
    it safe, the user action being to not interconnect with other commonly
    available items. As you say above, "Equipment makers are not liable
    for what users may WRONGLY do.....", but regulators are always
    interested in such things. They seem relaxed about the situation.

    snip
     
  11. Phil Allison

    Phil Allison Guest

    "Chris Jones"

    ** Then why keep moving the goal posts like is is one you cannot bear to
    loose ??



    ** If you mean that, then why make it impossible for anyone to answer you ?




    ......... Phil
     
  12. Phil Allison

    Phil Allison Guest

    "Malcolm Moore"
    "Phil Allison"

    ** The warning notice is not compulsory.

    Only the use of the "double square" symbol or the words "Double Insulated"
    are.


    ** The fact that a class 2 appliance must not be earthed.


    ** Huh ???

    What madman's logic is this ?

    What the hell do you think "X -rated " means ???



    ** Absolute drivel.

    Class 2 construction appliances are inherently much safer than class 1
    types.

    What users do that COMPROMISES that additional safety is beyond the control
    of makers or authorities.


    ** SFA they can do about it.

    The issue is one of legal liability on the part of someone who elects to
    earth a class 2 item.



    ......... Phil
     
  13. Phil Allison

    Phil Allison Guest

    "Chris Jones"

    ** Not just one device, but an entire hi-fi system INCLUDING the damn
    speakers !!!


    ** A third party could be the one electrocuted - maybe a small child.


    ** The makers of the class 2 devices are not liable in such a case.

    Their items are not permitted to be connected to the earth system of
    another.


    ** Millions of them around.

    Heaps of places sell 3 pin plugs to the public.


    ** The punishment for mis-wiring a plug ought not be the death of anyone.




    ** The most common cause of electrocution in the home is ( or was until
    recently) incorrectly wired plugs and extension leads.

    The worst electrocution trap in where BOTH miswired but BOTH work OK unless
    the two meet up.

    1. The extension lead has active and neutral wires reversed, earth is
    wired OK ( most consider this to be harmless).

    2. The appliance has earth and neutral wires reversed, active is on the
    correct pin ( appliance works fine in normal outlet).


    When appliance "2" meets lead " 1" ?????

    Death to a toddler.



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

    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.
    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.
    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
     
  15. Phil Allison

    Phil Allison Guest

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

    ** Of course there is !!

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




    ** There is.

    A Class 2 appliance must not be earthed.


    ** 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)



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

    ( snip more irrelevant drivel )


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




    ........ Phil
     
  16. Phil Allison

    Phil Allison Guest

    "Terry Given"


    ** Yawn .......

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




    ........ Phil
     
  17. You are correct for a transformer based power supply device such as a
    plug-pack, but this is not necessarily the case for other products. The
    deliniation between Class 1 and Class 2 is becoming very grey. Whereas AS3108
    and AS/NZS61558-1 say any transformer that has an earth terminal must be
    classified as Class 1 other standards do not.

    Definition and references below from AS/NZS60950-1, since I happen to be using
    it at the moment. Note the use of earthing is not prohibited, just that the
    safety strategy of the design must not rely on the protective earth. This
    standard might/is be used for a switch mode PSU plug-pack.

    =====
    "COPYRIGHT"
    1.2.4.2 CLASS II EQUIPMENT: Equipment in which protection against electric
    shock does not
    rely on BASIC INSULATION only,but in which additional safety precautions,such
    as DOUBLE
    INSULATION or REINFORCED INSULATION are provided,there being no reliance on
    protective
    earthing.
    =====

    There have been many changes since the old AS3108 and AS3100 type standards
    existed as the sole point of reference. None of those standards took into
    account EMC filtering or stray currents due to SMPSU, etc. With the more
    modern standards you can certainly use Class 2 construction, with functional
    (not protective) earthing. Note, connecting an earth does not automatically
    make it Class 1 in this standard.

    If you want to split hairs on the issue over the Class 2 box-in-box marking,
    perhaps I should of said before to scatch off the symbol. It is then
    functionally earthed Class 2 construction. It can only be truly Class 1 if the
    earthing is protective. There is no marking to define these products (yet).
    The mis-wiring of plugs etc is not a factor taken into consideration.

    Here is a reference from the same standard:

    ======
    "COPYRIGHT"
    2.6.2 Functional earthing
    If FUNCTIONAL EARTHING of accessible or other conductive parts is necessary,all
    of the
    following apply to the FUNCTIONAL EARTHING circuit:
    - the FUNCTIONAL EARTHING circuit shall be separated from parts at HAZARDOUS
    VOLTAGES
    in the equipment by either:
    ..DOUBLE INSULATION or REINFORCED INSULATION or
    .. a protectively earthed screen or another protectively earthed conductive
    part,
    separated from parts at HAZARDOUS VOLTAGES by at least BASIC INSULATION and
    - it is permitted to connect the FUNCTIONAL EARTHING circuit to a protective
    earth terminal
    or to a PROTECTIVE BONDING CONDUCTOR and

    1.0 sq mm for 10A cords up to 2 metres long and 1.5 sq mm for 10A cords longer
    than 2 metres.

    I did make a mistake with the multiplication factor, it is 1.5 and not 1.6
    times. I am not making it up - sometimes I think it would be easier to
    understand if I did. For functional earthing there is no size requirement
    other than that needed for it to do the intended job. For protective earthing
    and bonding you can provide the minimum conductor sizes in the standard (1.0 or
    1.5 sq mm), or use the minimum size conductor that meets the following:

    ==============
    "COPYRIGHT"
    2.6.3.3 Size of protective bonding conductors
    PROTECTIVE BONDING CONDUCTORS shall comply with one of the following:
    - the minimum conductor sizes in table 3B (see 3.2.5);or
    - the requirements of 2.6.3.4 and also,if the current rating of the circuit is
    more than
    16 A,with the minimum conductor sizes in table 2D;or
    -for components only,be not smaller than the conductors supplying power to the
    component.
    The current rating of the circuit used in table 2D and in the test of 2.6.3.4
    depends on the
    provision and location of overcurrent protective devices and shall be taken as
    the smaller of
    a)or b)as follows.
    a)The rating of an overcurrent protective device specified in the equipment
    installation
    instructions to be installed in the building installation wiring to protect the
    equipment.?47
    b)The rating of an overcurrent protective device in the equipment that protects
    the circuit
    or part required to be earthed.
    For PLUGGABLE EQUIPMENT TYPE A and if neither a)nor b)is applicable,the current
    rating of
    the circuit shall be taken as the RATED CURRENT of the equipment or 16
    A,whichever is
    greater.
    =================

    So (b) takes into account the rating of protective device that protects the
    circuit or part that needs to be protectively earthed. If a part that could
    fail to earth is protected by a 1A fuse then the protective conducter is sized
    to pass the following test, otherwise a great many PCB tracks that carry earth
    within a small SMPSU would be disallowed.

    If a series connected mains socket or device is protected by a (say) 5A fuse
    the intermediate bonding conductors to the equipment mounted socket outlet
    could be reduced in size accordingly. Fifteen years ago you couldn't do this,
    but you can now.

    This is the test for bonding conductors.
    =================
    The test current,duration of the test and test results are as follows:
    - if the current rating of the circuit under test is 16 A or less, the test
    current is 1,5 times the
    current rating of the circuit under test, the current is applied for 60 s and
    the resistance of
    the PROTECTIVE BONDING CONDUCTOR , calculated from the voltage drop,shall not
    exceed
    0,1 ?;
    =================

    There are many cases where AS3100 or AS3108 say a specific thing cannot be done
    but a more modern product specific standard may allow it, and AS/NZS3000 is no
    longer a prescriptive standard with regard to anything on the equipment side of
    the supply interface.

    The damn standards change so often it costs us thousands of dollars a year to
    keep up to date.
     
  18. 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.
     
  19. Phil Allison

    Phil Allison Guest

    "David, the pedantic FUCKWIT one.

    ** " No reliance " = NO connection to the AC supply earth system.


    WAKE UP FUCKHEAD:

    AS/NZ standards are for engineers and installers to heed.

    The issue here relates to *ordinary consumers* !!!

    Consumers are neither aware of nor need to follow published standards.

    The law of **negligence** certainly applies to them though.




    ** Blah, blah, blah - same as I said.

    Piss off - you damn IDIOT.



    ....... Phil
     
  20. Phil Allison

    Phil Allison Guest

    "Terry Given"

    = Kiwi ARSEHOLE & MASSIVE BUCKET

    " David, the pedantic FUCKWIT one."

    ** Yawn - none of it had ANY relevance at all.



    ** WAKE UP - YOU ASININE FUCKHEADS:

    AS/NZ standards are ONLY for engineers, manufacturers and installers to
    heed !!

    The potential shock hazard issue with class 2 and class items mixed in a
    home entertainment system is all about what *ordinary consumers* do - at
    home !!

    Ordinary consumers are NOT aware of nor need to consider published standards
    AT ALL !!

    The laws of **negligence** certainly applies to them though.

    Shame they does not apply to ANONYMOUS idiots posting dangerous CRAPOLOGY !





    ......... Phil
     
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