TV Power Cable Extension

[opps]

Nearly all the LED/LCD monitors in my workplace, have an earth connection - possibly (and I may be wrong!) because, if connected to a PC, the ground of the video cable would be earthed from the PC - any exposed shielding on the monitor would then be earthed anyway.
Even some monitors with an external PSU that would appear to be Class II, carry an earth through to the monitor.
...and some very strange external

Now think about it. The screens in question had a power brick (read: transformer). I guess that they weren't in fact earthed. The connection to the computer was not DVI., it was the royalty free version- "display port".

Laptops were used to send the signal to the screen. They are not earthed.

Sorry, not intentionally disagreeing with you. Sometimes I suspect that devices that look like they are earthed, might not always be. That said, desktop PCs often are, laptops, nearly never.

 

[JohnW2]

Aren't you contradicting yourself by saying there is nothing wrong with doing undesirable things.:

"Nothing wrong" in terms of the electrical safety of the item itself - but as 'undesirable' (if 'unnecessary') as having an earthed kitchen sink (which a pretty high proportion of metal ones are).

However, I've never seen instructions for a kitchen sink saying that it "MUST NOT be earthed".

Kind Regards, John

 

[RandomGrinch]

That said, desktop PCs often are, laptops, nearly never.

You may be surprised
For example, every Unibody MacBook (using the official MagSafe2 charger), is earthed through the PSU.

 

[JohnW2]

For example, every Unibody MacBook (using the official MagSafe2 charger), is earthed through the PSU.

What actually is earthed - do they have touchable conductive parts?

Kind Regards, John

 

[RandomGrinch]

What actually is earthed - do they have touchable conductive parts?

Kind Regards, John

Now you've got me questioning myself!
I was slightly wrong - I've only PATted the end of the charger cable which is earthed - however the MacBook body has 1k Ohm resistor between the AC Gnd and internal Gnd - enough to reduce any buzzing from the class Y cap.

 

[JohnW2]

Now you've got me questioning myself! ... I was slightly wrong - I've only PATted the end of the charger cable which is earthed - however the MacBook body has 1k Ohm resistor between the AC Gnd and internal Gnd - enough to reduce any buzzing from the class Y cap.

Fair enough, but I think my question remains -is that "internal Gnd" connected to any touchable conductive parts?

Kind Regards, John

 

[RandomGrinch]

Fair enough, but I think my question remains -is that "internal Gnd" connected to any touchable conductive parts?

The internal ground is connected to the anodised aluminium body of the MacBook - definitely touchable!

Although I doubt a basic insulation fail would allow it to become conductive.

On the other hand, if the charger was fake (not a MacBook charger, but you get the idea )...

 

[plugwash]

I don't recall ever seeing a CRT without an earth. The only LCD I can think of that had an earth was the really expensive one sent out to radiologists to work from home during covid.

In my experiance there is a massive distinction between monitors and TVs. Every CRT monitor (both video monitors and VGA/SVGA) monitors I can remember had an earth. TVs OTOH did not, at least in the sizes I encountered (granted I was not rich growing up, so most were 20 inch or less, maybe the really bit ones were different).

In the LCD era I would say that still most monitors had earths and most TVs didn't, but I recall more exceptions.

They had the kettle leads rather than the clover ones, but I am not sure if the earth ran back to the plug.

Cloverleaf has an earth. It's figure 8 that doesn't.

 

[RandomGrinch]

Every CRT monitor (both video monitors and VGA/SVGA) monitors I can remember had an earth.

Although some of ours had no exposed metal - the only way to PAT (apart from treating it as Class II), would be to probe the end of the D-Sub (although the resistance could be pretty poor), or stick a very long thin screwdriver down through a ventilation slot, onto the sheilding!

 

[plugwash]

Yeah, you see a similar thing with some modern power bricks for laptops and similar sized devices. They have an earth connection and presumably use it as part of their protection strategy but they have a floating output so there is no way to directly test earth continuity.

I wonder if "PAT testing" is a British oddity or if other countries do similar tests, and if so whether they encouter the same problems we do.

 

[JohnW2]

The internal ground is connected to the anodised aluminium body of the MacBook - definitely touchable!

Fair enough - that's the answer I was asking for. Never having owned (and rarely handled) a MacBook, I didn't know that they had a metal body.

Although I doubt a basic insulation fail would allow it to become conductive.

I'm not sure what you mean. 'Conductive' is conductive, and metal is conductive, regardless of any faults!

Kind Regards, John

 

[JohnW2]

Yeah, you see a similar thing with some modern power bricks for laptops and similar sized devices. They have an earth connection and presumably use it as part of their protection strategy but they have a floating output so there is no way to directly test earth continuity.

Quite - 'earth continuity' betyween what and what? If it has a floating output and (like every one I've seen) no external conductive parts, the concept of 'earth continuity' seems irrelevant/meaningless.

However, I believe that PATesting was invented by Mr Jobsworth

Kind Regards, John

 

[EFLImpudence]

I am not sure where this is going but my last TV, from 2009 I believe, a Samsung LE40B550 had an earth but no exposed metal.

My current TV does not have an earth.

 

[DetlefSchmitz]

I believe that PATesting was invented by Mr Jobsworth

Something I could agree with!

also FYI
In electrical safety testing, portable appliance testing (PAT, PAT inspection or PAT testing) is a process in the United Kingdom, Ireland, New Zealand and Australia

 

[RandomGrinch]

I'm not sure what you mean. 'Conductive' is conductive, and metal is conductive, regardless of any faults!

Sorry, I was overthinking your question, and thought you were relating it to the definition of an "Exposed-conductive part"