A friend of mine sent me this tube to try and get it running. Would anyone here happen to know what voltage these run at? I'm thinking 12-15kV.





Would be cool to see how it performs.

Holy crud. That’s cool.

Three stage too - A little better than the Kaktus tubes. Yeah, no more than 10-15kV, or 45kV per stage. Maybe even drop that back to 10Kv to avoid xrays. Unless you have an xray detector.

David

Thanks. I'll use 15kV or less and test for x-rays. Might try it with a PNV-57a psu. 57e apparently had nearly 20kV but i think the a-model has much less.

Keep in mind the voltage may be lower under load, and fly up under dark conditions -

So static tests alone may not account for everything safetywise.

Once you get close to 20K, you're in the danger zone.

David

I have no idea what i'm doing.

But i managed to build a transformer that turns 3V input into around 10Kv. Before i "touch off", is this even remotely how it should be wired up?

^   You the only one who might have an idea

@cj7hawk

This is a good question. Theoretically, each tube is individual, but collectively, I think the static field passes through the glass and the path to the nearest anode may be *through* the glass, causing a gating effect.

So you would need 3 x 15Kv PSU, separately decoupled or powered by different batteries, so that you can connect the tubes in series- That is to say something like this.

A<--C|A<--C|A<--C

45K-30K|30K-15K|15K-0K

So the total voltage potential is 45K, but is experienced as 15K between tubes, with the Anode (Screen) of one tube connected electrically to the (Photo)Cathode of the tube next to it.

Or 15K per tube, but not electrically coupled, so that they are floating, eg, 3 x PSU, 3 x Batteries, All disconnected from each other - So no connection between tubes - Though if the tubes charge up, they could cause their own fields to drift, which could be bad, so you'd still want to couple the Cathodes to the Anodes next to them.

Does the above make sense?

Regards
David

Pretty sure that wouldn't work. The American and Soviet cascade tube designs used a multistage voltage multiplier that developed ~45kV from end to end and the three tube sections were tied in at the right spots to get ~15kV across each tube. Having 15kV between the anode of one tube and the cathode of another seems like asking for trouble. Some of the American tubes used a fiber coupler between stages and a relatively large and thick chunk of glass like that still didn't have 15kV across it. The field gradient issues that cj7hawk alluded to only complicate the matter further.

This Soviet tube looks like it may not use a fiber coupler between stages. Some early designs used a thin (very thin) mica or glass disk with the photocathode on one side and the phosphor screen on the other though I don't know if that was only for early experimental tubes or if it ever went into production. That definitely won't take it.

Three independent 15kV supplies would, in a perfect theoretical world, work but don't try it in practice. At these potentials, you're bound to get corona discharges everywhere (notice how all the terminals on this tube are generously rounded) and unless the entire PS assembly, including battery and switch, is equally rounded/potted/insulated, it'll do what it wants and not what you want it to do. Plus it'll want to reach out and zap you for any reason.

Would recommend building a voltage multiplier that can reach 45kV overall and tap off at the right places for the tube. While it'd be nice to keep one end of the tube at ground potential (like near your eye), I'd consider driving the multiplier at the midpoint or at one of the tube stages. Your life will be much easier if the highest potential on any end of the tube to ground is 30kV or less. Above 30kV, it becomes very difficult to do anything without potting, oil submersion, or big rounded terminals. Remember that 30kV will easily jump more than an inch in air.

HV diodes for a multiplier are relatively cheap on eBay but stay away from the cheap HV disk caps from China unless you're willing to severely derate them. Had most of the Chinese special "30kV" caps short out internally around 20kV while submerged in an oil bath. The epoxy coating on them was applied improperly and didn't adhere to every point of the capacitor like a true conformal coating.

That does make sense. This would totally not work then. I'll upgrade the supply to one that can output at least 30kV and work out a way to divide it. Thanks for the info and suggestions.

No No No No No - Don't do that - That could be dangerous. Make sure there's never the potential for more than 15KV per stage.

You could use a ladder circuit at about 1Kv for the pump voltage, then you can use 1200V diodes and capacitors in the ladder ( as long as you make sure the peaks are < 1000V ) since no stage on the ladder will be more than 1000V.

Then after 15 increases, take your first tap, then after 15 more, your second, and 15 for your final.

Mentioning the ocular at 0v is a good idea that TXDX said.

Three power supplies is OK for an experiment - Just don't get close to it, keep the amps down with a big resistor and make sure they all have their own isolated battery.

High voltage is dangerous, but you can always get a good distance away and just watch for the green glow.  You'll need to pot it if you're going to make it fully operational.

David

I'm not going to go over 15kV per stage. I meant to divide the 30kV output into 0, 10, 20 and 30, so i can get 10 per stage. And then assemble as you suggested above.

And i'm an electrician so i'm fairly familiar with all kinds of zaps.

Cool - :) Please forgive the cautious tone then, if you're a sparky, you'll know where I'm coming from - :)

It is very difficult to divide 30Kv or 45Kv - There is no practical way to do it outside of resistors, and resistors will lose too much power at those voltages. And if you use active components and lose a stage, the voltage could end up being transferred to another stage and emitting xrays, was the basis of my thinking.

(though if you prove me wrong, I'll learn something new, and I'm far from an expert at those voltages)

David

Build 3 multipliers, run them from one driver.

This is what I did for a us 3 stage tube years back.

You will need to insulate very well. I used hv potting compound.