[morzh]

Well, in a way.....transformerless radios are usually not heavy drawers.

However the sole criterion is: do not exceed any of your winding's current rating.
If your 6.3V winding IS a 20A capable one....sure! Use it!
But somehow I doubt this is the case.

Remember: a transformer is a power transfer (or impedance matching) device - it keeps the power constant plus the core and resistance losses.
So ideally, your 100 Watts travels across the two as 100 Watts, and in every winding it is the constant power. You draw 100 Watts from your 120V output, it is 0.85A in both input and output but it is 19.5A in between where you use 6.3V ones.

[skyscraper]

But even running a very modest 20 watt aa5, that's 4 amps across the 5v winding. Those are almost universally 2 amps for rectifier tubes, are they not?

[klondike98]

Yes the ValueTronics equipment is used equipment. Its where I bought my isolation transform, a similar model the the one I posted. When I first started this hobby (I'm not like a lot of you folks, electronics is a later in life interest) I wanted this safety item to be something checked by someone who knows what they are doing, although I realize its pretty straight forward piece of equipment. They have LOTS of used equipment, some newer, some vintage.

[morzh]

In very large radios those could be more....in something like 20-70-90 I think this is about it. Though in them sometimes 4 24 tubes are in parallel and this gives you 7A but then it is only 2.5V.

[Mr Grumpy]

Thank you all so much for your responses. - Amazing link klondike98 - And thanks for the direction morzh.
I have no idea what all the transformer talk is about, I still haven't read my copy of 'Elements of Servicing'
that was pointed out by another awesome phorum member.

[morzh]

Grumpy

To summarize, Tab suggested building a transformer using two step-downs as he has done.
We explained how this method might be limited in power below what could be required for a tube radio.

[Mr Grumpy]

Thanks morzh.

I'll probably go with the Dale or Fluke that you have and will PM you when it arrives for the jumper info.

[morzh]

The other 300VA was not a bad choice either if it is guaranteed.
I am happy with the FLuke.

[Warren]

Yes, I am thinking about getting that same one you suggested Morzh. If i do I will PM you for the jumer info also if ok. Thanks, Warren

[morzh]

Sure.

[Joeztech]

I remember getting a filament transformer when I was in high school to operate a late 40s Buick radio in the house. The filament transformer had to be rated at 6.3VAC filament output that was better than the expected DC amp input to the original vibrator power circuit in the Buick radio. The car radio was permeability tuned and really solid with two 6V6GT tubes in a parallel single ended output stage. It was a great performing radio bought cheap at a wrecking yard. It turned out to be a rather large filament transformer in order to handle powering the entire car radio, but worked well. At the cost of heavy current filament transformers these days it would probably just be less expensive to buy an isolation transformer that was designed to do just that function with wattage rating adequate to handle any AC/DC chassis you expect to work on. The 300-400 watt range should handle just about any radio you would encounter. Many radios draw less than 200 watts power from the 120VAC line.

The main thing is to consider your own safety above all else. Don't get yourself into a dangerous situation. A known good isolation transformer is a worthwhile expense when your life is at risk.

Joe

Joe

Joe

[morzh]

When your life is at risk an AK47 is a worthwhile expense. With a standard clip and some rounds.

[Mr Grumpy]

Reviving a really old thread, but I finally bought this Isolation transformer and am ready to go.

...except for the fear of death by electric shock...

Is there a way to test this thing to ease my fear?  Do I hook it all up and then throw screwdrivers
at the set from a safe distance until something trips?

Thanks again.
Vince

[morzh]

This is a Fluke and is same type I have except for two outlets (I have 4).

The ultimate test is a Hi-pot.
Short of this simply measure resistance from BOTH output L and N to input L, N and Earth. There should be no continuity and no DC leakage.
If it is like it was in mine, it ould be a "leakage reduction" device which has a jumper from output N to Earth GND which is simply removed then.

[OZ4]

Mr Grumpy
Here's my two cents.

To test a transformer for leakage just plug into a functioning GFI outlet. That would protect you.

And sizing a transformer- they are rated in VA thats volt amps. Kinda like watts only slightly down rated.

On using two identical power transformers connected back to back- the total power would be shared between all the windings. Just be sure to check that the voltages match and all the windings are all in phase.

Sorry if I state the obvious.
Happy sparking everyone