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Power - Earth-RCD's- ISO/TX's and workshops.

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Red_to_Black
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We had one about that size at the first TV repair shop I worked at, the one I have now is only a baby portable one, not sure of it's rating as the plate is missing, probably about 250 VA.
ttt:

 
Posted : 11/04/2014 4:30 pm
Refugee
(@refugee)
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My bench has the earlier 1000VA lump that RS used to sell that came in a steel box with lugs to bolt it down even though it is so heavy that it will not move anyway.

 
Posted : 11/04/2014 5:32 pm
Refugee
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Mine is staying on the floor with the nice big metered Variac up at bench level.

 
Posted : 11/04/2014 5:49 pm
Terrykc
(@terrykc)
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I'm thinking of hanging my 40lb lump of ISO TX from the underside of my bench. I'd better make sure it's well secure :ccf

What's the matter with the floor? (Standing on not hanging from!!!)

The further you can keep the electro-magnetic field of the transformer from sensitive equipment, the better. I'm particularly thinking of shadow-mask tubes here ...

When all else fails, read the instructions

 
Posted : 11/04/2014 5:53 pm
Refugee
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Mine is at the back of a cable storage area with a bench power supply and Variac 3 feet above it.
There is a Trinitron screen 6 feet above.

 
Posted : 11/04/2014 6:54 pm
Anonymous
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Having read the many discussions in this thread and elsewhere I came to the conclusion the the safest method of using an isolation transformer is one per bench and only one item connected to it(only my opinion) From this I realised that when an earthed instrument is connected to the chassis of a live chassis set any shock hazard protection is lost. That led me to wonder if an RCD could be added to the transformer output then some protection could be regained.

Experiments showed that the RCD would not trip. I could understand that but could not work out in a real installation. Jeffrey made a comment that made it all clear. The earth neutral link needs to be upstream of the RCD and not downstream as would be the case with a scope connected to chassis.

Another great idea consigned to the bin. I think I will go back to playing with Leggo. :aai :cca

Al

 
Posted : 11/04/2014 11:38 pm
Anonymous
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Yes. you got it nailed now. The isolation transformer is just turning a something with no mains transformer into a device with one so you can pick an arbitrary point in that device under test and connect that point to "earth". Hence they can't be shared.

 
Posted : 12/04/2014 2:11 am
Mark Hennessy
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All of this is explained in a BBC EGN - point 3 is explained with diagrams in Appendix 1

http://www.bbc.co.uk/safety/pdf/safety- ... v2-1nm.pdf

Did anyone download this EGN(4) as it no longer seems to be available from the BBC?

Al

https://dl.dropboxusercontent.com/u/990 ... former.pdf

All the best,

Mark

 
Posted : 07/05/2014 11:58 pm
Anonymous
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Mark, thanks for the link.

Al

 
Posted : 08/05/2014 12:19 am
Rebel Rafter
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Hi, everyone, RR here again. I'm not qualified to give proper advice about mains earthing, that seems to be a subject on it's own. But one thing I would recommend if you haven't done it already is if you're working in a remote shed, as a friend of mine does, then you should definitely have some kind of emergency back up lighting, like the ones in screwfix for instance, just in case you're using say a hot soldering iron in the darkness hours and the power trips out, you could get badly burnt if you suddenly can't see what you're doing. My mate fixes motorbikes in his shed so I fixed him up with an emergency light as he handles petrol out there, as well as having engines running, etc., with hot exhausts amongst other things. RR.

 
Posted : 17/12/2014 9:14 pm
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