Variac question

On Thursday, 8 November 2018 23:51:21 UTC, Phil Allison wrote:

tabby wrote:
Phil Allison wrote:



Well, they were standard & widespread in the 1990s.

** Live chassis tube TVs and radios " standard & widespread " in the 1990s ????

Live chassis TVs were very common in the 90s.


** But not TUBE sets as the above requires.

Pretty much ALL TVs were CRT in the 90s.

I have a 1990s 12 inch GE color portable where the whole chassis is live and only isolated by the antenna balun.


FYI:

The OP did NIT even mention "live chassis" so his post was wrong and so is yours.

I was responding to your mention of 'hot chassis' not the OP's.
What the OP mentioned is irrelevant.


** Bullshit. I was responding to the OP post - so what he wrote is totally relevant.

get a grip

Contemporary use of 1:1 isolation transformers would be for
servicing devices like SMPSs.


It removes the direct path to ground of the electrical power,
significantly reducing the chance of death.

** That is wrong.

Using an isolation transformer allows one to connect the common
rail ( or any other point) of an off-line SMPS to safety ground.
After which you can use a scope in the normal way to investigate
various waveforms, maybe small ones like MOSFET drive signals.


One can, but they are also used to reduce shock risk.


** Biggest safety myth out.

Using an isolation transformer unnecessarily INCREASES electric shock risk.

The UK government certainly disagrees with you.

** More arrogant bullshit.

it's why they're mandated in bathrooms

We have used isolation transformers for decades in bathrooms ....

** FFS you congenital context shifimg **bullshitter **

- the TOPIC here is electronics servicing with an Iso in the AC supply!!!!!!

the principle is the exact same, namely that after an iso one would need to touch 2 parts of a circuit to get a shock not just 1.


NT

Go away, stay there.


.... Phil

 

On Friday, 9 November 2018 00:08:03 UTC, Phil Allison wrote:

tabby wrote:



There are unique conditions in which an isolation transformer
does not prevent the risk of electric shock.
Therefore they increase the risk of electric shock.

** What I wrote was that if the use of an iso tranny is not essential, you are better off not using one and taking all the usual precautions instead.

This detailed article by Rod Elliot explains why using an iso is hazardous - not that reading it will have the slightest impact on wooden heads like you or NT.

http://sound.whsites.net/articles/iso-xfmr.htm

an article with a lot of errors & dubious assumptions, as a result of which he comes to wrong conclusions. If I get the time I'll go through it.

FYI:

The use of an RCD, ELCB or other earth leakage detector ( aka safety switch) on a workbench is a safety essential.

I fixed lots of TVs with no such 'essential'. Most were live chassis. Any sensible person would advise using one now, but essential? We just used what was available & affordable at the time.


NT

 

[Phil Allison]

tabb...@gmail.com wrote:

Phil Allison wrote:
tabby wrote:



There are unique conditions in which an isolation transformer
does not prevent the risk of electric shock.
Therefore they increase the risk of electric shock.

** What I wrote was that if the use of an iso tranny is not essential,
you are better off not using one and taking all the usual precautions
instead.

This detailed article by Rod Elliot explains why using an iso is
hazardous - not that reading it will have the slightest impact
on wooden heads like you or NT.

http://sound.whsites.net/articles/iso-xfmr.htm


an article with a lot of errors & dubious assumptions,

** All your posts are like that - but not the above.

If I get the time I'll go through it.

** The context shifting bullshitter has not even read it.

Yawwwnnnn.......

FYI:

The use of an RCD, ELCB or other earth leakage detector ( aka safety
switch) on a workbench is a safety essential.


I fixed lots of TVs with no such 'essential'. Most were live chassis.
Any sensible person would advise using one now, but essential?

** Try learning to read sometime - the phrase was "safety essential."

Obviously your life is not worth much.


...... Phil

 

On Friday, 9 November 2018 06:10:01 UTC, Phil Allison wrote:

tabby wrote:
Phil Allison wrote:

This detailed article by Rod Elliot explains why using an iso is
hazardous - not that reading it will have the slightest impact
on wooden heads like you or NT.

http://sound.whsites.net/articles/iso-xfmr.htm


an article with a lot of errors & dubious assumptions,


** All your posts are like that - but not the above.


If I get the time I'll go through it.



** The context shifting bullshitter has not even read it.

Yawwwnnnn.......

ok, I won't waste my time on you.

 

[three_jeeps]

On Thursday, November 8, 2018 at 7:08:03 PM UTC-5, Phil Allison wrote:

tabb...@gmail.com wrote:



There are unique conditions in which an isolation transformer
does not prevent the risk of electric shock.
Therefore they increase the risk of electric shock.



** What I wrote was that if the use of an iso tranny is not essential, you are better off not using one and taking all the usual precautions instead.

This detailed article by Rod Elliot explains why using an iso is hazardous - not that reading it will have the slightest impact on wooden heads like you or NT.

http://sound.whsites.net/articles/iso-xfmr.htm

FYI:

The use of an RCD, ELCB or other earth leakage detector ( aka safety switch) on a workbench is a safety essential.


.... Phil

I think the point in this thread is that one has to know what they are dealing with before employing an isolation transformer. I read the article. IMO, the article title is an attention getting and his point is that the isolation transformer presents a 'false sense of safety'. The assumption that most ppl will make is that one blindly needs to install an isolation xformer in all applications and it will keep you safe. There are limitations based on the circuits one is dealing with.
The assertion to be safe one must "use of an RCD, ELCB or other earth leakage detector" is a general statement but also a bit misleading. RCDs are NOT recommended and ELCBs are essential. This article explains things quite well..
https://www.linkedin.com/pulse/what-difference-between-mcb-mccb-elcb-rccb-elcab-engineers

The statement about live chassis 'only in TV of the 90's' is grossly incorrect.
My father owned/operated a TV/Radio sales and service shop from early 50 through 2000. I grew up in the shop and serviced TVs and other electronic gear from the 60, 70, and 80s. I can attest that the live chassis was not only in the 90's. I've seen it in the 70s and 80's TVs. I've also seen it in electronic gear in the 2010s - e.g. soldering stations/hot air rework stations from China, as well as three voltage power supplies from China.
Point is, one needs to be aware of the realities of the circuitry they are working on and dont blindly apply 'safety measures'...that doesn't mean to ignore them. It means to apply them but know what areas of 'safety' they are meant to protect.

 

On Friday, 9 November 2018 17:43:53 UTC, three_jeeps wrote:


> I think the point in this thread is that one has to know what they are dealing with before employing an isolation transformer. I read the article. IMO, the article title is an attention getting and his point is that the isolation transformer presents a 'false sense of safety'. The assumption that most ppl will make is that one blindly needs to install an isolation xformer in all applications and it will keep you safe. There are limitations based on the circuits one is dealing with.

To remain safe when working on live equipment one needs to understand what one is dealing with whatever safety systems are in use. Isos have their limitations of course, so do all safety methods.

> The assertion to be safe one must "use of an RCD, ELCB or other earth leakage detector" is a general statement but also a bit misleading. RCDs are NOT recommended and ELCBs are essential.

Woah. Voltage operated ELCBs are obsolete, a known hazard and offer no protection whatever against shock when working on a live chassis appliance. They only protect against the earth system becoming live as a result of a high current fault (not via a human) that would otherwise raise the earth system above 50v. That's all they do. They were obsolete in the 1980s. Current operated ELCBs _are_ RCDs.

This article explains things quite well..
https://www.linkedin.com/pulse/what-difference-between-mcb-mccb-elcb-rccb-elcab-engineers

It's yet another article with both correct points and some confusion.

The statement about live chassis 'only in TV of the 90's' is grossly incorrect.
My father owned/operated a TV/Radio sales and service shop from early 50 through 2000. I grew up in the shop and serviced TVs and other electronic gear from the 60, 70, and 80s. I can attest that the live chassis was not only in the 90's. I've seen it in the 70s and 80's TVs. I've also seen it in electronic gear in the 2010s - e.g. soldering stations/hot air rework stations from China, as well as three voltage power supplies from China.

Unless I'm mistaken I don't think anyone said live chassis kit only existed from the 90s. I have had live chassis stuff from post-2000, 90s, 80s, 70s, 60s, 50s, 40s, 30s, 20s and one item that might have been from the 10s or 20s. By the time you go that far back 'live chassis' becomes somewhat meaningless in that it was normal to have live bits all hanging out.

> Point is, one needs to be aware of the realities of the circuitry they are working on and dont blindly apply 'safety measures'...that doesn't mean to ignore them. It means to apply them but know what areas of 'safety' they are meant to protect.

that of course is vital when working on live equipment. Anyone that does so without understanding what they're doing or gets careless is in trouble. In about of 99.2% of those cases a shock awakes them to the need to be sensible. Mortality is somewhere roughly in the region of 1 per 600 shocks.

There is NO safety system that can protect people against that. RCDs offer zero protection against shock from transformer derived B+, don't protect against L-N shocks and don't always work on L-E shocks. ELCBs offer no shock protection at all from live working hazards. Isos offer limited protection. Never touching the equipment with both hands offers limited protection. An earth-free workzone offers limited protection, etc etc. Sometimes you just need to know what you're doing or not do it.


NT

 

[Phil Allison]

three_jeeps wrote:

** What I wrote was that if the use of an iso tranny is not essential,
you are better off not using one and taking all the usual precautions
instead.

This detailed article by Rod Elliot explains why using an iso is
hazardous - not that reading it will have the slightest impact on
wooden heads like you or NT.

http://sound.whsites.net/articles/iso-xfmr.htm

FYI:

The use of an RCD, ELCB or other earth leakage detector
( aka safety switch) on a workbench is a safety essential.



I think the point in this thread is that one has to know what they are dealing with before employing an isolation transformer.

** Which practically counts out the servicing equipment with unknown faults..

I read the article.

** Good for you.

IMO, the article title is an attention getting and his point is that the isolation transformer presents a 'false sense of safety'. The assumption that most ppl will make is that one blindly needs to install an isolation xformer in all applications and it will keep you safe. There are limitations based on the circuits one is dealing with.

The assertion to be safe one must "use of an RCD, ELCB or other earth leakage detector" is a general statement but also a bit misleading. RCDs are NOT recommended and ELCBs are essential.

** The use of RCDs is highly recommended in the article *YOU* cited !!!!

QUOTE:

" RCDs are an extremely effective form of shock protection "
------------------------------------------------------------

https://www.linkedin.com/pulse/what-difference-between-mcb-mccb-elcb-rccb-elcab-engineers


The statement about live chassis 'only in TV of the 90's' is grossly
incorrect.

** Good - cos no-one here actually said that.

Do you have a reading disability ??

Never mind, NG postings are notorious for being confusing & difficult to follow.



..... Phil

 

[Lucifer]

On Thu, 8 Nov 2018 19:09:09 -0800 (PST), tabbypurr@gmail.com wrote:

On Friday, 9 November 2018 00:08:03 UTC, Phil Allison wrote:
tabby wrote:



There are unique conditions in which an isolation transformer
does not prevent the risk of electric shock.
Therefore they increase the risk of electric shock.

** What I wrote was that if the use of an iso tranny is not essential,
you are better off not using one and taking all the usual precautions instead.

This detailed article by Rod Elliot explains why using an iso is hazardous -
not that reading it will have the slightest impact on wooden heads like you
or NT.

http://sound.whsites.net/articles/iso-xfmr.htm

an article with a lot of errors & dubious assumptions, as a result of
which he comes to wrong conclusions. If I get the time I'll go through
it.

One error is where he writes,
"Without isolation, you know exactly what is dangerous at all times.
It's quite apparent that you can't touch anything that's at mains
potential,"

That's poor English. Obviously you can touch anything that's at
mains potential but you shouldn't.

FYI:

The use of an RCD, ELCB or other earth leakage detector ( aka safety
switch) on a workbench is a safety essential.

I fixed lots of TVs with no such 'essential'. Most were live chassis.
Any sensible person would advise using one now, but essential? We
just used what was available & affordable at the time.

NT

 

On Saturday, 24 November 2018 15:35:25 UTC, Lucifer wrote:

On Thu, 8 Nov 2018 19:09:09 -0800 (PST), tabbypurr wrote:
On Friday, 9 November 2018 00:08:03 UTC, Phil Allison wrote:
tabby wrote:

This detailed article by Rod Elliot explains why using an iso is hazardous -
not that reading it will have the slightest impact on wooden heads like you
or NT.

http://sound.whsites.net/articles/iso-xfmr.htm

an article with a lot of errors & dubious assumptions, as a result of
which he comes to wrong conclusions. If I get the time I'll go through
it.

One error is where he writes,
"Without isolation, you know exactly what is dangerous at all times.
It's quite apparent that you can't touch anything that's at mains
potential,"

That's poor English. Obviously you can touch anything that's at
mains potential but you shouldn't.

one of too many errors in that article.


NT

 

[Phil Allison]

Lucifer wrote:

This detailed article by Rod Elliot explains why using an iso is hazardous
not that reading it will have the slightest impact on wooden heads like you
or NT.

http://sound.whsites.net/articles/iso-xfmr.htm


One error is where he writes,

"Without isolation, you know exactly what is dangerous at all times.
It's quite apparent that you can't touch anything that's at mains
potential,"

That's poor English.

** The English grammar is fine and there is no technical error.

Obviously you can touch anything that's at mains potential but you shouldn't.

** Wot pedantic twaddle, the word "safely" in front of the word "touch" is understood from general context.


..... Phil

 

[peter wieck]

There are times when I am told: But, you know what I mean!

To which the only valid answer is: No, I know what you said (wrote). I am still trying to discern what you mean.

Be very, very careful about making assumptions in a technical discussion, and in using any of poor grammar, syntax, word-choice, punctuation or spelling. The consequences may be significant - and surprising.

Peter Wieck
Melrose Park, PA