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Re: Christmas Comes Early!

Posted: Sat Jun 17, 2017 4:00 am
by Garrett Young
Did you pull pin 7 low?

I've powered my fusor with this supply at 50kV/12mA. The HV cable is a non-standard length between the threaded connection and the internal high voltage terminal. In addition, the pin diameter needs to be smaller than the standard Spellman cable. I just mocked something up with some high voltage wire 2mm bullet terminal and a liberal amount of silicone grease.

Re: Christmas Comes Early!

Posted: Sat Jun 17, 2017 4:24 am
by ian_krase
Wait, a 2mm bullet? I just used a banana and it seemed to work. And yes, I used the PL259+hugelongcablebanana type arrangement.

I was able to use corona (I think it's corona?) to light a small flashlamp from several inches away. No vacuum chamber to test on, of course, and not quite sure what to do about the corona since I don't have any metal balls.

The real question is what is up with my voltage monitor. My 10 volt meter (galvanometer style, tested) barely deflected at all. As far as I can tell, TP3 (which is before the voltage monitor buffer) outputs 10V just fine but somehow R31 (and nothing else) drops this down more than 10x.

Re: Christmas Comes Early!

Posted: Sat Jun 17, 2017 4:41 am
by Garrett Young
I think a standard banana plug is too large to actually engage (at least it seemed to me). That may be why you are hearing some cracking. Silicone grease may help.

What is the full scale current of your meter? If the meter is 10V FS and 1mA FS then it should work because the output impedance is 10kohm. If the FS current is higher than 1mA then it will not deflect appropriately.

I'm not sure what you mean about interlock to a plugged in cable, because that doesn't seem to be present in the schematic and mine doesn't operate that way.

Re: Christmas Comes Early!

Posted: Sat Jun 17, 2017 5:04 am
by ian_krase
That is exactly the problem. And I paid 8 bucks for the thing! My meter has an impedance of less than a kilohm!

I think that the corona noise is at the end of my cable. Not sure. Any suggestions on how to locate it?

I guess I need to add an op amp buffer to drive the meter. I considered shorting out the 10K resistors but it looks like the LF444 degrades significantly as it reaches the needed currents.

Re: Christmas Comes Early!

Posted: Sat Jun 17, 2017 5:16 am
by Garrett Young
Turn off the lights and you may be able to see where the corona is happening.

Re: Christmas Comes Early!

Posted: Sat Jun 17, 2017 4:32 pm
by Garrett Young
Correction: Standard banana does work.

I'm now offering a high voltage cable (2.5 ft.) and all of the high power mods for $300 +shipping (including the price of the supply)

PTV50N200X2947 power supplies

Posted: Mon Jun 19, 2017 6:46 am
by ian_krase
How are you making the cable that's for sale? Does it have a shield?

The corona (I assume) was more hissing than cracking.


Anyway I got mine completely working, with my front-end and my op-amp boosters all set up.

And then I tested it out, and something rather scary happened.


I had the PSU sitting on a table, with the (roughly 3-4 foot long) HV cable going out to the right where it was held pointing up using a clamp. I had the grounded case of the supply attached via wire to a pin at the end of a nice long nonconducting rod, to which I attached one end of a neon flashlamp tube with the other pin sticking out. My body was always at least 500mm away from any high voltage conductor (other than that inside the ground-shielded cable) and my body was not grounded by any method (wearing rubber-soled shoes, standing on a non-conductive floor, not touching anything else.


I turned the PSU up to the point where corona hissing was audible, then brought the flashlamp on the end of the chicken stick nearer the HV terminal, at which point it illuminated. I moved it away, and of course it went out.

Then I touched the PSU case (to turn it off!) and got a shock. Not a really painful one, more like a really bad getting-out-of-the-car or touching-the-doornob one.


Did my body get electrostatically charged up by the corona? Or is something else bad happening that isn't solved by the grounding of the case?

Re: Christmas Comes Early!

Posted: Mon Jun 19, 2017 9:43 am
by John Futter
yup
charged up!!
it hurts
but doesn't kill

Re: Christmas Comes Early!

Posted: Mon Jun 19, 2017 3:33 pm
by Richard Hull
Naked high voltage, in air, with or without major corona will always charge nearby insulated items. (induction).... To what level? It depends on the surface area and leakage rate of the isotrpic capacity. In general, a human, no matter how well insulated, is a really leaky isotropic capacity due to the fine tips of hair, mainly on the arms. If the hair on the head starts to stand up, you are really leaky but have acquired a rather huge charge. If you are on a concrete floor such a charge will blow through your shoes and should you survive, it will hurt.

I have felt myself charging near a Spellman 120kv ladder stack in "lifter" experiments. If this happens, you are too close to the source. Back off and let yourself leak, naturally....No one enjoys an electrical shock, even a mild one. Even a tesla coil at high frequency can charge nearby items via corona or an almost touching arc. (ionic rectification through air)

Richard Hull

Re: Christmas Comes Early!

Posted: Mon Jun 19, 2017 7:49 pm
by ian_krase
Yikes. Can we have an FAQ about this type of hazard?

Also, how can one detect the lower levels of this? Can one discharge safely through a large resistor? Is it mitigated by faraday-caging everything?