And you should be.

It can be worked safely if you follow necessary precautions, but unless you are familiar with those, better follow the disclaimer and "do not try this at home".

The main issue is that capacitors keep their charge after unplugging, so you might have some that are still dangerously charged.

I remember when opening old CRT TVs they had a big notice inside about discharging them before servicing some parts of the circuit.

A good GFCI, safety equipment and respect go a long way.

Especially the first one saved me more than a dozen times at this point. Yay for required-by-law GFCI on the house-level.

I also do recommend to get some Schuko (CEE 7/3 and CEE7/4) or UK plugs and sockets, even if you're in the US just so you can avoid the safety nightmare that is the US plug. (Thuogh I'm not sure if you can do them as permanent installs in the US... they're still neat for lab equipment)

edit: you should have respect for anything about 50V or so, after that point it can be quite dangerous. 120V is way above where i start using safety equipment.

No GFCI will save you on the secondary side of a transformer. My point is: working with standard 120/230V requires just following codes and guidelines. Tinkering with HV in non-standard setups requires understanding of how and why.

The secondary side of a transformer can be a lot safer if there is no potential to ground. If there is the GFCI will trigger.

But yes, working with codes and guidelines is the best option here.

There is always potential for ground. The secondary side of the transformer has a much more dangerous potential: a unknown fault puts something at ground, and then thinking there is no ground you touch ground and the other side. Normally that would be harmless, but since there is an unknown ground it is deadly.

In many ways mains power would be safer if there was no ground, and a lot cheaper. However a couple failure cases are even worse without ground, and they are the type you only find out about when somebody dies. Thus we put ground in houses.

You might get silly and insert more than one hand into a working device.

I don't get silly above 50V.

edit: also, in case you put two hands in a device, it won't matter much if it's on the other side of an isolating transformer or not. The GFCI might not trigger in this case.

> also, in case you put two hands in a device, it won't matter much if it's on the other side of an isolating transformer or not. The GFCI might not trigger in this case.

That was my point.

You almost killed yourself over a dozen times, but your advice to the inexperienced person above is a few safety tips, not much better “just be careful”.

The only reasonable advice is to not even touch the stuff unless you’re an expert with plenty of training. Especially since there’s nothing to be gained except satisfying a useless curiosity.

I almost killed myself over a dozen times and yet I'm still standing. If you don't take advice about handling high electricity from someone who experienced it a couple times, from whom do you take it then?

I will gladly touch stuff to change my lightbulb, I'm not gonna consult an expert for that. Or swapping fuses and other, similarly, simple procedures that are reasonably safe if you are "just careful".

Useless curiosity is where the majority of human progress comes from.

Where do you see advice of "just be careful"?

Without useless curiosity HN wouldn't exist...

Waay too boring following the safety police rules.

Playing with HV can be fun, just build fly swatter-level inverters instead of using a transformer/capacitors big enough to kill you.

A CCFL inverter from an LCD screen is a good start, you can light neon bulbs and gets ozone

those are dangerous too--they output high frequency AC which can cause burns. with a thumb-sized CCFL supply i once burned a tiny hole in my finger. never bled a drop since the current cauterized it but it hurt for a week.

You can burn yourself with a soldering iron or splashed solder too, better avoid electronics all together.

The fact that you can burn yourself with soldering iron is mostly obvious. That CCFL inverter can easily burn hole through you finger without you noticing it until it's too late is not that obvious.

You'll live.

In both cases with overwhelming probability. But there is difference: you have to be extraordinary clumsy to get life-threatening burn from soldering iron, but you can get life threatening burn from HF HV very easily.

Not from a CCFL inverter, you won't.

This thread serves as a great example of why it's not a good idea to plaster dire warning labels all over everything on the planet "just to be safe." When everything is dangerous, nothing is.

50 Volts and the right conditions can kill you just fine. Always be careful.

you've got to be very careful and never use HV without treating it with respect. i use the one hand rule extensively, keeping my left hand firmly tucked behind my back while the supply is turned on.

1000V, at the current levels needed for this application, amounts to the juice behind a good carpet shock.

Dunno about the Monoscope in particular, but a lot of tubes need several milliamps, which is quite a bit more painful than a good carpet shock. Not fatal, but not something I'm eager to experience. And I'm the guy who used a one-henry inductor to administer electric shocks to people in high school — including, repeatedly, myself.

The issue is that it's a lot easier to build or buy a kilovolt power supply that doesn't have adequate current limiting than one that does. And even one that has it in theory may not have it in practice — that big capacitor across the output? Make sure it isn't just wired directly to the output terminals, because its ESR sure as hell isn't going to be adequate current limiting.

So I think it's reasonable to be wary of kilovolt circuits. Dying is easy, but you only get to try it once.

Lightedman's dead comment, in response to my, "The issue is that it's a lot easier to build or buy a kilovolt power supply that doesn't have adequate current limiting than one that does," said, "You can buy Van de Graaf generators all day long. Quarter-million volts minimum for $200."

While van de Graaff generators are indeed relatively affordable, and indeed some even cost less than US$200, a working microwave oven costs US$60, and a broken one can be had for under US$10. Furthermore, a safe van de Graaff generator is not actually capable of supplying enough current at the high voltage to operate a vacuum tube, while a deadly microwave-oven transformer is; and there are orders of magnitude more microwave ovens available.

A KV from a half decent supply will throw you across the room in a bad case and give you a nasty burn in a slightly better one. Don't underestimate the power of a HV supply, especially one that has some nice stabilization and caps.

my power supply is capable of 1KV at 10mA. it's the one piece of lab equipment i own that genuinely scares me. all this stuff has to be treated with respect. still though it's good for cool experiments with monoscope tubes. :-)

In other news, you don't need 100 watts worth of HV to run a CRT.