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Fusion Success with Precipitator Power Supply

Posted: Mon Jul 22, 2019 11:57 pm
by Mark Rowley
After suffering the typical setbacks with using insufficient XRTs, I recalled several folks here discussing the cheap precipitator power supplies. Back in 2017, Finn Hammer conducted a very thorough review of the dual transformer 30ma / 30kv unit (pictured). Heres the link to Finn's excellent report: ... ply#p77914

It was suggested that it may be good for a demo fusor and I recall reading about at least one group member using one to create a basic demo unit. Other than some periodic discussion, there wasn't much more about said about it.

Since I was mentally gearing up for a costly road trip to obtain a big heavy transformer, I decided to give Finn's unit a test with my system. Figured I had nothing to loose for a $50.00 investment and if it didn't work I could use it for other HV projects.

TBH, when it arrived skepticism was running high. Not only was it light and comparatively small, I was also expecting the overcurrent shutdown issues everyone discussed in previous threads.

So off I went to run another 220v line to the Fusor and to source a plexiglass platform for it to temporarily rest upon. Once done and energized, it produced a nice stable plasmoid. In fact, I had to quickly turn it down as the grid was getting red hot due to the 100mTorr pressure in the chamber. Obviously, lack of current was not going to pose much of an issue (at least for my small fusor).

After getting the diff pump running and the vacuum at suitable "fusion levels" I began running it through the paces. It became immediately apparent that it easily provides the current and voltages I need for the 2.75" fusor.

The plasma picture below was powered by this supply. The pic was taken at 27.5kV / 2.85ma / 35mTorr of Deuterium. The only reason I didn't push it to a higher current was due to the grid getting too hot (I'm still learning to slowly walk this thing up to higher levels). And once again I have to emphasize, no overcurrent shut down. And as Finn indicated earlier, this unit barely gets warm.

One concern that Finn brought up was potential flashover at voltages over 20kV. I have yet to power this up without a load (and may never do so), but when operating under load there's no telltale corona hiss or warning signs when going over 20kV. For a brief time I pushed it up to 32kV or so and may have heard a little hissing but nothing of great concern. I would suspect the 60kV unit may prove to be more of a concern but I have no plans on operating in that region. And if someone wanted to pot this in oil or silicone rubber, that would easily remove most of the concern.

In the next week or so I will be testing the larger 4 transformer 10ma / 60kV unit. I'll add to this post when it arrives.

Overall, I think this is a great entry level power supply for the Fusor enthusiast. It may not come close to breaking any records, but for $50 one cannot loose.

I'm looking forward to seeing more folks testing these supplies and pushing them to their limits.

Mark Rowley

Re: Fusion Success with Precipitator Power Supply

Posted: Tue Jul 23, 2019 12:40 pm
by Dennis P Brown
Good post. I was wondering, Finn was worried about arc over on the board by the HV above 20 kV. Was this an issue or did you put the unit under oil?

Also, could you show more details on the construction of your measurement devices for the voltage and current outputs? That would be useful for others here as well.

Finally, could you post on both your neutron detector setup and deuterium supply (assuming you haven't already) in more detail, too? These be of interest here relative to your setup. I assume you already posted details on your chamber.

Re: Fusion Success with Precipitator Power Supply

Posted: Wed Jul 24, 2019 7:39 pm
by ian_krase
This seems like it may be a game changer.

I'd be very interested in any details about wiring and schematic.

Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 1:19 am
by Mark Rowley
Specific to the 30kV version, there’s not much to wiring it up. Its output is completely isolated / floating, just like a battery. So it’s basically a matter of thoroughly grounding the anode and routing the cathode to the grid. Wiring the voltage and amperage meters is just as shown in the FAQ’s. Nothing new there.

Powering requiriments of the supply is standard household 220ac.

I haven’t tested the 60kv version yet but I suspect wiring will be similar if not identical. As noted before, you’d be taking chances running it up to 60kv without potting it in oil or similar.

Mark Rowley

Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 2:48 am
by Rex Allers
Great to hear that someone with some basic electric sense was able to finally put one of these supplies to good use.

I've only looked at the listings a while back. Am I correct that the pic with 2 HV transformers is the 30 kV version and 4 transformers will be 60 kV?

My guess is every transformer has a rectifier in series in it to make DC out. Does that sound right from what you know?

I always thought the biggest drawback for US users was the need for 220 VAC input. I wonder if they could be hacked to take 120 VAC input? I assume that like most switchers the input gets rectified to some high DC voltage that gets switched into the HV transformer primary. You probably never had any reason to check but I wonder if you can measure the DC voltage being switched on the board?

I'm wondering if hacking the input circuits could allow them to run with 120 by having a doubler configuration (if it isn't already doubled from 220).

Anyway congrats again for being the first to successfully use one of these supplies.

Maybe I should order my own and try it rather than just sitting here and speculating.

Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 4:38 am
by Richard Hull
If Rex is right,

1. Is the rectifier in backwards in these potted flybacks? (making the output negative). Thus far I have only seen 100% of these putting out a positive HV.

2. if just positive output, is the entire output two terminal floating and not grounded. This would allow you to ground the positive side.

I know that if you place a huge order for negative output flybacks someone will make them for you. ($$$$$$)
Of course just wire flybacks with no rectification will allow you to externally rectify to you hearts content.

Serial connecting floating flyback rectifier combos would create insulation issues, but spacing out the HV side and conformal coatings could offer a win.

I never poo-poo'd these supplies. Finn gave a good stab at this, but then he told us he would disappear for a time and hoped to return. His splendid efforts here are missed. The smaller cross fusors tend to get results at a bit lower voltages due to the pressures at which they are worked. I guess if all you want is a cheap highway to do fusion and get in the neutron club these supplies in crosses might do the trick. I watch all such efforts in these smaller systems to see how far they can advance on extremely low budgets. Joe Gayo is doing great, but has plus ultra gear in abundance.

Richard Hull

Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 4:52 am
by ian_krase
Wait, you mean this thing can do either polarity just by selecting what becomes the ground??? Now that is interesting. I smell an accelerator project...

Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 5:48 am
by Mark Rowley
It's still baffling to me how folks will build a neutron producing Fusor (some being top notch) and then abandon the whole shebang after making the club. In all respects, this should be a new beginning. Lots more to do and learn. For me, this small scale platform allows things like grid design experimentation, power supply testing, D2O electrolysis improvement, video monitoring of the poisser, and neutron yield improvement.

On a side note, I attempted unsuccessfully to address a typo on the original post. The PSU was incorrectly listed as 30ma / 30kv. Its supposed to be 10ma / 30kv.

Ian, you and several others have mentioned the possibility of applying these to accelerator use. I think this is a great idea...especially with the 60kv unit.

I'll be posting more numbers soon. Need to finish a painting project first.

Mark Rowley

Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 9:35 am
by Dennis P Brown
The 220 volt service really shouldn't be an issue: most homes have 220 v service for their dryer and/or hot water heater (all main panels have this service - just two out of phase 120's.) An electrician could easily add an outlet if anyone wanted that in a given room (I easily added my own outlet for 220 service in my project room but I am experienced in wiring. Just remember, follow all State regulations relative to code and associate local law, first.)

Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 7:25 pm
by John Futter
For a precipitator you need floating outputs so you should be able to wire either way by grounding whichever