Safety ?

[west_nm]

I am starting to collect the things required to work on tube amplifiers. I've read some interesting things about isolation (?) transformers .

Any suggestions for safely using one? I became aware of them after reading your safety sticky.

Is an Ultra Isolator from Topaz what I'm looking for?


Regards,


Steve

[Tom Bavis]

Instead think about installing a small isolation transformer into any transformerless amp you work on - then it will be safe AFTER it leaves your bench... they're about $15 - a small price for safety...

You don't need an isolation transfomrer for amps that have a power transformer - though I use my capacitor tester to check for line-chassis isolation (insulation resistance function) before I plug in any unknown piece of equipment. I often find a leaky line-chassis capacitor - there's a reason they're called the "death cap".

[west_nm]

I may not have understood the use of a Isolation Transformer.

Worst case scenario: I'm standing in a puddle of water in my bare feet. I would never.
Will having my amp plugged into an Isolation Transformer be safer if I were to touch it?

Forgive the stupid question.


Steve

[SY]

What you need is any sort of power transformer (which is generally the case) AND the ground wire from the mains (green) FIRMLY tied to the chassis.

You might consider using a variac; it provides no isolation (that's the job of your power transformer) but allows you to slowly ramp up the voltages and catch mistakes before they become explosions.

[Jacques Merde]

Originally Posted by west_nm

I may not have understood the use of a Isolation Transformer.

Worst case scenario: I'm standing in a puddle of water in my bare feet. I would never.
Will having my amp plugged into an Isolation Transformer be safer if I were to touch it?

Forgive the stupid question.


Steve

No.

[west_nm]

Originally Posted by SY

What you need is any sort of power transformer (which is generally the case) AND the ground wire from the mains (green) FIRMLY tied to the chassis.

You might consider using a variac; it provides no isolation (that's the job of your power transformer) but allows you to slowly ramp up the voltages and catch mistakes before they become explosions.

A variac is plugged into the transformer now. It (variac) is old and has no earth ground. I will remedy this with a proper power cord and receptacle.
Thank you for the clarification.

I asked about Transformer Isolation on another site and was basically laughed at. I take safety seriously.

Thanks everyone for taking the time to answer. You may have saved a life.


Steve

[ArtG]

One additional step may be worth your consideration, following SY's good advice. It's a good idea to be certain that your AC wall outlets are wired correctly. The green ground wire will be ineffective unless it's actually connected to ground. For $5 or less there are small "plug in" wiring testers, available at electrical supply houses and hardware stores. They are usually yellow and have three small indicator lights on the body, which will display wiring faults. I've used one for over 25 years, and have found serious errors in places that I would not expect them!

[benb]

Electric Receptacle Tester
Electrical Receptacle Tester with GFCI Diagnosis

[kevinkr]

Once you have verified things are effectively grounded protecting all outlets on your bench with a GFCI/GFI may also save your bacon..

[west_nm]

Thanks for the tips.

I have a Furman product that lets me know the condition of the AC input.
It covers : open ground, open hot, open neutral, hot ground reversed and hot neutral reversed. Everything is plugged into a GFI.

Will you tell me the best way to shunt a cap to discharge the stored energy? I still get (low) voltage readings 16hrs later. I'm not sure what value resister to use.

Regards,


Steve