• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

01A question

Toroids should also have better leakage inductance than EIs, but EIs do have better PRI→SEC leakage capacitance than unscreened toroids, so they still have a place for some positions.

Looking around, another option is the Triad VPM series. These toroids are designed for medical applications, and have a primary-shield that can be connected to PE (earth). The screening brings a defined-maximum earth-leakage current of 10µA @264Vrms, so it should be <5µA for 120VAC Line.

There's a 240V rms secondary, the VPM240-420

VPM Series general lineup

They also have a custom windings page, so you should be able to get one for the Plate supply you need:
Triad Custom page

would be interesting to learn about anyone's experiences with these; but the low leakage current indicates likely good noise screening.

Triad (Perris, CA) still has at least some U.S. manufacturing; maybe that woud make custom PTs a practical option. It might well be worth giving them a call and giving them a target specification. After all, they do boast about history in Audio.
 
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Thanks Rod.

The Triad VPM and Antek look quite similar in that they both have the shield that can be connected to earth. Comparable VA weight is more for the Antek's and the price roughly 50% less for the Antek. Also Antek has an additional 6.3V secondary winding while the Triad VPM does not. Anyway good to learn about the Triad option.
nash
 
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Hey all, I have a question akin to the original question this thread was created for. A while back I bought a tube lot that had a pair of the weirdest 01A's I've ever seen. They are labeled as "Continental Electronic Co. Cetron CE-201-A". They are globe shaped, but are MUCH larger than standard globe 01As. They are even larger than my globe 45 tubes!

They also looked like they had condensation inside them, so for a while I just assumed they had a crack somewhere and were dead. However, looking at them again, that "condensation" is actually little beads of metal. I can get them to detach from the glass if I flick the tube. If I didn't know any better, I'd almost say that these are actually mercury vapor rectifiers. But I can't find anything online about these since they're labeled as 201A, and the only results I can find are for standard 201A tubes.

Attached is a few pics of them, as well as one comparing it to a globe 45 and standard globe 01A. Does anyone know for sure what this is?

IMG_20221222_082337_labeled.png IMG_20230326_084404.jpg IMG_20221222_073539.jpg IMG_20221222_073605.jpg
 
You can do a couple of simple test to determine if they are or not vers of 01A.
Need a LV PS of abou 6V, One Amp. On the heater / filament terminals apply LV thru some kind of limiting restor
Does anyone know for sure what this is?
You can do a couple of simple tests to determine if those tubes are or not some vers of the 01A. Or DOA.

You will need a LV PS of about 12V, One Amp. I keep a discarded but still good auto battery under the bench for these kind of tests.

On the heater / filament terminals apply LV thru some kind of limiting resistor like 50R. If the filament is 5V, 0.25 A a VM across the filament terminals will settle at something like 3.5-4V. If the VM indicates much lower the tube is probably gassy & can’t warm up. Or might be a Hg rectifier.

If the tube passes that test, then apply 5V thru a suitable resistor to the filament. To check for gas apply ~100V thru a current limiting resistor of 100K to the plate while the grid is tied to the filament. If a VM connected to the plate settles at 8V you have a gas rectifier. Something like 50V might be a good indicator, you’ve got a tube that works.

Early members of the 01A family had One amp filaments until better cathode emission materials were developed.

For a very good account of how the 01A family & vacuum tubes in general were developed in vest in a copy of Gerald Tyne’s ‘Saga of the Vacuum Tube’.
 

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