isolation transformer needed

"mike the madman "

** Like being able to safety ground the chassis, speakers and tuner box of a TV set that otherwise all sit at lethal voltages. ** Yep - never use one if the unit already has one. ** Pure insanity.

** Any sane tech will simply ground the common ( negative line ) in the high voltage part of the PSU.

Then proceed as usual for units that have internal isolation trannys.

** Totally insane BOLLOCKS.

** Something only rabid lunatics like mike do.

Yawnnnnnnnnnnn........

** Used examples sell for around $US1000 through on-line dealers.

More utter insanity.

** Wot a posturing, bullshit artist. ** Wot an obvious pile of crapology.

Typical of mug, 5V engineers way out of their depth.

..... Phil

Creative snipping eh?

Isolation"

through

but

On an isolation transformer (single phase), the primary side is always grounded because the neutral leg is always bonded in the distribution panel. This is a code requirement. If the secondary is also grounded (I am pretty sure this is also a requirement), the two sides are still electrically isolated. The current leaving the secondary hot leg must return to the neutral (grounded) leg of the secondary. There is no path from the secondary hot to the primary neutral. The secondary has to leave the hot leg and return on the secondary neutral leg. The secondary current cannot go any where except through secondary loop. Any noise on the high side (from nearby VFDs or other) must pass through the primary winding in order to induce a current onto the secondary. The winding itself is a low pass filter, so much of the noise on the primary is dissipated as heat.

"Andy the Honky "

** No way is it a requirement for 1:1 mains transformers used for " safety isolation " or electrical / electronic servicing.

When you have no clue - shut the f*ck up.

This is NOT an opinion forum for morons.

Despite appearances.....

.... Phil

If your mains supply has one side grounded, then touching the 'live' side causes a shock. If you use an isolating transformer, you can touch either leg safely. That plus an RCD feeding it provides the best degree of safety in the workshop. I'm surprised you don't see this.

--
*Wrinkled was not one of the things I wanted to be when I grew up

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

"Dave Plowman (Nutcase)"

** Not if **anything** is earthing one of them - like a scope or other test equipment ground.

Or an unknown fault in the equipment.

** Appalling BULLSHIT !!!

Once you add an isolation tranny in the AC supply

- RCDs do NOT work anymore !!!!

---------------------------------------------

Wot an ignorant pommy turd to say otherwise.

** No surprise to anyone that Dave Fuckwit Powman is full of SHIT up to his eyeballs.

The notion he describes is 100% FALSE and totally discredited many decades ago as a very DANGEROUS practice.

.... Phil

Isn't that obvious?

Err, no. The whole idea of an isolating transformer is to isolate any such faults.

But it won't do any harm...

You really should seek treatment. Preferably by connecting yourself across any mains supply. Especially two phase.

--
*If you try to fail and succeed, which have you done? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

"Dave Plowman (Nutcase)"

** Not if **anything** is earthing one of them - like a scope or other test equipment ground.

Or an unknown fault in the equipment grounds the incoming AC or something linked to it.

** Appalling BULLSHIT !!!

Once you add an isolation tranny in the AC supply

- RCDs do NOT work anymore !!!!

---------------------------------------------

Wot an PIG ignorant pommy turd to say otherwise.

That insane notion will KILL someone !!!!

** No surprise to anyone that Dave Fuckwit Powman is full of SHIT up to his eyeballs.

The notion he describes is 100% FALSE and totally discredited many decades ago as a very DANGEROUS practice.

Dave can go rot in HELL.

.... Phil

You amaze me. You're so bent on proving me wrong that you are not open to the possibility that applying logic to misguided advice might yield useful information.

Normally, I'd not waste my time trying to train internet denizens. But in cases where a plethora of misguided advice presented vehemently and with AUTHORITY puts people at risk of DEATH, I feel compelled to speak up. This stuff hangs around for years.

So, back to your statement...with logic...

If you "touch" only one thing, it doesn't matter whether you have an isolation transformer or not. Problem is that touching one thing provides no information beyond what you could get using an insulated tool. You really don't need to "touch" anything.

Electricity finds it's way to touch you through paths you didn't anticipate.

How many of you woke up on the morning of your electrocution and said, "today, I think I'll electrocute myself"? Raise your hands high...oh, those of you who committed suicide by electrocution can put your hands down.

This is the important part...my contribution to the thread... Pay attention now:

The primary reason to want an isolation transformer to troubleshoot a power supply is to work on the primary side. Now, the KEY word is TROUBLESHOOT. What that means is that the power supply has a FAULT in the primary circuit. What's the fault? You don't know, or you'd just fix it. How safe is it to troubleshoot that particular fault? You don't know, 'cause you don't know what it is.

You're gonna RISK ELECTROCUTION based on the misguided assumption that an isolation transformer keeps you safe. YOU'RE NOT SAFE. YOU DON'T HAVE ANY IDEA WHAT THE PRIMARY CIRCUIT IS, BECAUSE IT'S NOT AS DESIGNED. IT HAS A FAULT!!!!!!! The node that the designer called common may not be common at all. IT HAS A FAULT!!!! You should not arbitrarily ground ANY node. It has a fault!!! (I'm skipping over the obvious question, "what is ground anyway?")

An isolation transformer is not inherently bad. It can provide a layer of protection. What is bad is the FALSE sense of security that the transformer makes it safe to poke around inside a supply WITH A PRIMARY FAULT.

I'll say it one more time.

I don't care if you design power supplies in your sleep. A FAILED power supply DOES NOT have the circuit that was intended. It has a FAULT. A safety analysis based on a working power supply and an isolation transformer DOES NOT APPLY. Maybe you've always been lucky. That's no cause to suggest to another that they can do what you've been doing and NOT DIE.

Then don't do that. People like you shouldn't mess with electricity.

--
*He who laughs last, thinks slowest.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

And you still haven't learnt anything, obviously.

--
*There are two kinds of pedestrians... the quick and the dead.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Out of your Topamax again?

Yes you do give very bad advice.

I've got no objection to anyone saying I'm wrong. Provided they back it up with facts. Mains electricity is always dangerous. Using an isolation transformer can *reduce* that hazard. Not *eliminate* it. And as regards connecting a grounded mains 'scope probe etc to equipment under repair which you've fed via an isolating transformer - words fail me. Someone that thick that they don't understand the safety issues should stick to playing with themselves - like Phil.

--
*Dancing is a perpendicular expression of a horizontal desire *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

"David Nebenzahl"

** Scumbags like YOU need a bullet in the head.

.... Phil

p

Dave, You seem to loack a basic understanding of isolation transformers and service techniques. The isolation transformer allows you to scope probe at any part of the circuit and create a "virtual ground" anywhere in the circuit. Isolation transformers do not eliminate shock hazard but are a very usefull tool on the service bench. If used by someone with the KNOWLEDGE to use it. . .

There is no reason to have the 'ground' on your scope connected to actual ground - with a suitable 'scope. Or perhaps you ground one leg of your DVM?

You seem to lack basic understanding of safe working practices.

--
*Do paediatricians play miniature golf on Wednesdays?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Have you ever worked on a piece of equipment ?

Certainly not effectively !

Certainly not safely !

Of course.

Really?

Perhaps you could give the reasons why things *must* be grounded under all circumstances. If you actually understand the dangers of this, of course.

--
*If at first you do succeed, try not to look too astonished.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.