Isolation transformer

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moggi1964

moggi1964

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Joined 2010

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moggi1964

moggi1964

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Joined 2010
So $60 got me the above product. It is brand new and still sealed in it's packaging.

I have one question that follows from this text from the manual:

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"Transformer [FONT=GMDBO A+ Times,GMDBO A+ Times][FONT=GMDBO A+ Times,GMDBO A+ Times]Plug the AC power cords of your equipment into your isolation transformer. Do not use extension cords or adapters that eliminate the connection to ground. Connect equipment that requires a external connection to ground to the isolation transformer’s potential equalization conductor,labeled "" on the unit."[/FONT][/FONT]
[FONT=GMDBO A+ Times,GMDBO A+ Times][FONT=GMDBO A+ Times,GMDBO A+ Times][/FONT][/FONT]
[FONT=GMDBO A+ Times,GMDBO A+ Times][FONT=GMDBO A+ Times,GMDBO A+ Times][/FONT][/FONT]
[FONT=GMDBO A+ Times,GMDBO A+ Times][FONT=GMDBO A+ Times,GMDBO A+ Times]Does this mean that one could plug a scope into this particular outlet (the one with the potential equalization conductor) without the fear of it becoming live or should I stick to plugging the scope directly into the wall socket?[/FONT][/FONT]
[FONT=GMDBO A+ Times,GMDBO A+ Times][FONT=GMDBO A+ Times,GMDBO A+ Times][/FONT][/FONT]
[FONT=GMDBO A+ Times,GMDBO A+ Times][FONT=GMDBO A+ Times,GMDBO A+ Times]Thanks.
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C

ChrisA

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Joined 2008
moggi1964 said:
Would this make a suitable isolation transformer to help beef up the safety of my DIY TSE tube amplifier build?

PowerVar 0 5 Power Conditioner Toroid Isolation Transformer w 6 Outlets 500VA | eBay

Thanks.
Click to expand...

People have addressed the question of "Would this make a suitable isolation transformer" but it's really not clear at all how an isolation transformer would "beef up the safety of my DIY TSE tube amplifier build".

I assume you have a standard design amplifier that uses a commercial power transformer and you don't have anything like a hot chassis or a mains voltage series string heater loop.

If you are worried about safety the main things to do are (1) all the wiring indie a metal chassis with a metal cover plate, (2) ground the metal chassis to the third conductor of the AC poet cord and (3) build an enclosure that covers the vacuum tubes and keeps them from being knocked, bumped or whatever. This could be a simple metal cage or a furniture grade cabinet.

If you have done all of the above, and you are using a conventional power transformer, it is hard to see why adding an isolation transformer will make the amplifier more safe.

Most people skip #3 because it adds nothing to the sound is the hard to make. But in the tube era, back when cars had no seat belts,had single cylinder brakes and not safety glass radio makers would not think of selling bare chassis with exposed tubes, it is just to dangerous and exposed them to liability.
 
moggi1964

moggi1964

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Joined 2010
I'm thinking more of the breadboard stage before all the chassis parts are put in place.

Wanting to be sure that if I make an error or there is a fault somewhere that a hot chassis isn't created. I appreciate that the IT isn't a be all and end all of safety and I can still create a path to earth myself but it's an additional layer at the testing phase.
 
C

ChrisA

Member
Joined 2008
moggi1964 said:
I'm thinking more of the breadboard stage before all the chassis parts are put in place.

Wanting to be sure that if I make an error or there is a fault somewhere that a hot chassis isn't created. I appreciate that the IT isn't a be all and end all of safety and I can still create a path to earth myself but it's an additional layer at the testing phase.
Click to expand...

If your breadboard contains a power transformer then you have the same isolation. Isolation transformers are not magic they are just like power transformers only the turns ratio is 1:1. using a 1:1 or a 1:4 is not a lot different.

If you want safety from accident then use a GFCI outlet. These add much greater safety and don't cost so much.

But with power am pliers there is this problem with filter capacitors. Even if you un plug the amp from mains power and ground the chassis you still can get a really bad shock. What I do is current contrastuction I pace a low vale "bleeder" resistor across the filter caps. This will quickly discharge the caps. then after the amp is working I clip this resister out and have one that is much larger value
 
moggi1964

moggi1964

Member
Joined 2010
I have a GFCI too :)

I also have rigged up a light-bulb based bleeder to discharge caps and will be running with multimeters constantly connected to B+ B- and a couple of other points.

Oh and did I mention the variac :D Not of course for safety as such but an early smoke detector!
 
2

29285

Disabled Account
Joined 2010
This looks a bit strange to me. Whenever I connect some live circuitry to an isolation transformer, I want a "floating" primary.
This may be a smps under test or an oscilloscope as well.
And the isolation transformer does NOT provide any protected earth terminal but a 2-pole AC-outlet.
 
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