Was everything switched off as you actually made the connection?
Everything that is only double insulated rather than earthed should
really be switched off as you make the connection.

--

Brian Gregory (In the UK).

To email me remove the letter vee.

"Brian Gregory [UK]" wrote in message
...
Was everything switched off as you actually made the connection?
Everything that is only double insulated rather than earthed should
really be switched off as you make the connection.

--

Brian Gregory (In the UK).

To email me remove the letter vee.


Both computer and video were off as when previously using the TV out option
on other occasions. I turned on the video and then the computer as
instructed
in the manual. Windows booted up, the monitor screen went blank when I
selected the ATI TV symbol, the system froze, I had to use the reset
button.
Derek.

That's just a crash.

I was meaning when things "blew up".

--

Brian Gregory (In the UK).

To email me remove the letter vee.

"Brian Gregory [UK]" wrote in message
...
That's just a crash.

I was meaning when things "blew up".

--

Brian Gregory (In the UK).

To email me remove the letter vee.


One and the same incident with the graphics card and video. When it happened
years ago with the TV and the HI Fi they were both swiched on.
Derek.

In articles (various) re apparent problem.

1/ As mentioned previously, most domestic appliances (TVs etc category)
are 2-wire connected.
These devices therefore have a 'chassis' of MID VOLTAGE ie 115V (230-0 /2)
which is not what most would consider 'earth' potential - as in the 3rd
pin.
(The 'chassis' is connected via high-impedance to the power supply, to
stop it floating in total isolation, uncontrollably.)
((PPS The London UNDERGROUND RAILWAY has its centre and side conductors
'tied' to the running rails in a similar manner - one is +400, the other
is -200 I think, and was the cause of a fire when at 2 places within the
same power section, both supplies became directly (shorted) to the running
rails many years ago (Wood Green - Cockfosters section??)

2/ Some domestic equipment, such as computers, increasingly connected into
the system, conventionally use 3-wire connections in the UK - ie the
chassis is at earth potential.

If/when 2-wire and 3-wire devices are connected together, the ''chassis''
can be at different voltages (115V difference) and therefore a small
current can flow between them on ANY connecting leads used:

The currents are SMALL and, apparently considered quite safe (to humans -
presumably with dry hand and not applied directly across the heart 8-),
because of the high impedance connection in each device to the mains
supply (about 10 000 000 ohms?) - however these currents may prove to be
too much for some electronic devices -

They may also take one by surprise if holding a lead when connecting such
equipment together!!!!! - albeit not fatal unless you step back and trip
over something dangerous behind you 8-)

This is why the instructions always tell you to SWITCHOFF the devices
before plugging them together!

However, with the mixture of 3 and 2 wire devices, there will always be
the possibility / probability of such 'leakage' current, and this might
therefore find itself using 1 of the 2 wires L/N in device (A), but the
Earth wire in device (B) - resulting in an imbalance in current
consumption between Live and Neutral (due to the amount going via Earth of
device B), and this could trip a sensitive RCCB (Residual Current Circuit
Breaker) - a possibility which increases as more devices are connected or
plugged in*

*Switch mode power supplies and their startuup current surges being a
likely cause of tripping the breaker


Phil

--
Phil Spiegelhalter:
==== Technical Training for Broadcasters =====
*RE CUE Mobile DV Multi-Camera Production and Non-Linear Editing*

"Phil" wrote in message
...
In articles (various) re apparent problem.

1/ As mentioned previously, most domestic appliances (TVs etc category)
are 2-wire connected.
These devices therefore have a 'chassis' of MID VOLTAGE ie 115V (230-0 /2)
which is not what most would consider 'earth' potential - as in the 3rd
pin.
(The 'chassis' is connected via high-impedance to the power supply, to
stop it floating in total isolation, uncontrollably.)
((PPS The London UNDERGROUND RAILWAY has its centre and side conductors
'tied' to the running rails in a similar manner - one is +400, the other
is -200 I think, and was the cause of a fire when at 2 places within the
same power section, both supplies became directly (shorted) to the running
rails many years ago (Wood Green - Cockfosters section??)

2/ Some domestic equipment, such as computers, increasingly connected into
the system, conventionally use 3-wire connections in the UK - ie the
chassis is at earth potential.

If/when 2-wire and 3-wire devices are connected together, the ''chassis''
can be at different voltages (115V difference) and therefore a small
current can flow between them on ANY connecting leads used:

The currents are SMALL and, apparently considered quite safe (to humans -
presumably with dry hand and not applied directly across the heart 8-),
because of the high impedance connection in each device to the mains
supply (about 10 000 000 ohms?) - however these currents may prove to be
too much for some electronic devices -

They may also take one by surprise if holding a lead when connecting such
equipment together!!!!! - albeit not fatal unless you step back and trip
over something dangerous behind you 8-)

This is why the instructions always tell you to SWITCHOFF the devices
before plugging them together!

However, with the mixture of 3 and 2 wire devices, there will always be
the possibility / probability of such 'leakage' current, and this might
therefore find itself using 1 of the 2 wires L/N in device (A), but the
Earth wire in device (B) - resulting in an imbalance in current
consumption between Live and Neutral (due to the amount going via Earth of
device B), and this could trip a sensitive RCCB (Residual Current Circuit
Breaker) - a possibility which increases as more devices are connected or
plugged in*

*Switch mode power supplies and their startuup current surges being a
likely cause of tripping the breaker


Phil

--
Phil Spiegelhalter:
==== Technical Training for Broadcasters =====
*RE CUE Mobile DV Multi-Camera Production and Non-Linear Editing*


We never really know if items we buy are 2 or 3 wire devices as most now
come with a moulded plug.
I told the supplier of my problem and he is happy to replace it. I will
report if the next one goes the same way!
Derek.

Phil wrote:

2/ Some domestic equipment, such as computers, increasingly connected
into the system, conventionally use 3-wire connections in the UK - ie
the chassis is at earth potential.

If/when 2-wire and 3-wire devices are connected together, the
''chassis'' can be at different voltages (115V difference) and
therefore a small current can flow between them on ANY connecting
leads used:

The currents are SMALL and, apparently considered quite safe (to
humans - presumably with dry hand and not applied directly across the
heart 8-), because of the high impedance connection in each device to
the mains supply (about 10 000 000 ohms?) - however these currents
may prove to be too much for some electronic devices -

They may also take one by surprise if holding a lead when connecting
such equipment together!!!!! - albeit not fatal unless you step back
and trip over something dangerous behind you 8-)

Yes, I get this. My computer has a tv card. The aerial lead to the TV
card always generates a spark when connecting to the PC. At the other
end of the aerial lead (eventually) is a sky receiver downstairs.
Connected to the same TV that that sky receiver is connected to is a DVD
player which is double insulated and not earthed. If I unplug the DVD
player from the mains, I no longer get the sparks! And if I don't, and I
happen to be touching the pc case and the coax plug at the same time and
forget what is about to happen, the very very minor shock takes me by
suprise.

Interestingly, although the DVD player is double insulated, it does have
an earth screw terminal on the back. Maybe I should earth it to
something :)

In article ,
Derek F wrote:


We never really know if items we buy are 2 or 3 wire devices as most now
come with a moulded plug.
I told the supplier of my problem and he is happy to replace it. I will
report if the next one goes the same way!
Derek.

Phil: 2-wire usually has a flat flex from the plug, and 3-wire a round
(circular) flex. Also there should be an indication of 'double insulated'
(possibly) on the equipment, if it is so constructed.

It is the mixture of types in an interconnected chain that is most likely,
IMO, to cause the problem

--
Phil Spiegelhalter:
==== Technical Training for Broadcasters =====
*RE CUE Mobile DV Multi-Camera Production and Non-Linear Editing*

In article ,
letters desk wrote:
Phil wrote:

2/ Some domestic equipment, such as computers, increasingly connected
into the system, conventionally use 3-wire connections in the UK - ie
the chassis is at earth potential.

If/when 2-wire and 3-wire devices are connected together, the
''chassis'' can be at different voltages (115V difference) and
therefore a small current can flow between them on ANY connecting
leads used:

The currents are SMALL and, apparently considered quite safe (to
humans - presumably with dry hand and not applied directly across the
heart 8-), because of the high impedance connection in each device to
the mains supply (about 10 000 000 ohms?) - however these currents
may prove to be too much for some electronic devices -

They may also take one by surprise if holding a lead when connecting
such equipment together!!!!! - albeit not fatal unless you step back
and trip over something dangerous behind you 8-)

Yes, I get this. My computer has a tv card. The aerial lead to the TV
card always generates a spark when connecting to the PC. At the other
end of the aerial lead (eventually) is a sky receiver downstairs.
Connected to the same TV that that sky receiver is connected to is a DVD
player which is double insulated and not earthed. If I unplug the DVD
player from the mains, I no longer get the sparks! And if I don't, and I
happen to be touching the pc case and the coax plug at the same time and
forget what is about to happen, the very very minor shock takes me by
suprise.

Interestingly, although the DVD player is double insulated, it does have
an earth screw terminal on the back. Maybe I should earth it to
something :)

Phil: An 'earth screw' or a chassis ground screw?????

--
Phil Spiegelhalter:
==== Technical Training for Broadcasters =====
*RE CUE Mobile DV Multi-Camera Production and Non-Linear Editing*

Phil wrote:
In article ,
letters desk wrote:
Phil wrote:

2/ Some domestic equipment, such as computers, increasingly
connected into the system, conventionally use 3-wire connections in
the UK - ie the chassis is at earth potential.

If/when 2-wire and 3-wire devices are connected together, the
''chassis'' can be at different voltages (115V difference) and
therefore a small current can flow between them on ANY connecting
leads used:

The currents are SMALL and, apparently considered quite safe (to
humans - presumably with dry hand and not applied directly across
the heart 8-), because of the high impedance connection in each
device to the mains supply (about 10 000 000 ohms?) - however these
currents may prove to be too much for some electronic devices -

They may also take one by surprise if holding a lead when connecting
such equipment together!!!!! - albeit not fatal unless you step back
and trip over something dangerous behind you 8-)

Yes, I get this. My computer has a tv card. The aerial lead to the TV
card always generates a spark when connecting to the PC. At the other
end of the aerial lead (eventually) is a sky receiver downstairs.
Connected to the same TV that that sky receiver is connected to is a
DVD player which is double insulated and not earthed. If I unplug
the DVD player from the mains, I no longer get the sparks! And if I
don't, and I happen to be touching the pc case and the coax plug at
the same time and forget what is about to happen, the very very
minor shock takes me by suprise.

Interestingly, although the DVD player is double insulated, it does
have an earth screw terminal on the back. Maybe I should earth it to
something :)

Phil: An 'earth screw' or a chassis ground screw?????

A machine screw complete with 3 washers going into the back panel, with
an earth symbol next to it.