New Fusor: progress

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Dennis P Brown
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New Fusor: progress

Post by Dennis P Brown »

Decided to start a new thread that is more relevant (title wise) since I have the new fusor chamber.

I'm continuing to strip down my old fusor for parts and adding both these items and other systems to the new chamber.

I installed the dry air system. This is not really necessary for a fusor but it was a complete unit I used for my high vacuum system. Its purpose is for slowing the turbo (via that special port located on the side of the turbo. Near the center of that first photo.) This shortens the time interval that the turbo bearing is under maximum strain forces.

I added the deuterium gas flow control system and my small deuterium lecture bottle.

Finally, I realize the interface plate I made for that old system can be used to help couple between my new electrode and an ISO 8 inch flange. It will still require some further work but being aluminum it will be rather easy to machine. Also, the plate already has both the required large O-ring seal and a proper sized access port that ready accepts a KF 80 O-ring gasket system (Easier to couple to my electrode via parts I have). So this flange is 80% complete for my electrode to fit an ISO plate that I have located (of course, one buys what's cheap and the plate has an access port that requires a 100 mm copper gasket. Not something I can easily interface to and requires gaskets I don't want to use.)

So, the new system is progressing. Hope this week to get time to machine the required parts so that the electrode can properly be attached to my fusor chamber. Also, I need to construct a new fusor anode 'cage'. Then a vacuum check (and dealing with massive out gassing issues ... ) and if I can get into the low micron range, first light (under 20 kV, no deuterium.)

If this works (and I manage to activate silver) I will not need my old diffusion pump and its butterfly gate valve. So stripping that system is not important. But we will see.
Attachments
Dry air system: valve, piping, and dryer. Upper right
Dry air system: valve, piping, and dryer. Upper right
Deuterium feed system: micro-flow control valve, piping and lecture bottle
Deuterium feed system: micro-flow control valve, piping and lecture bottle
Aluminum Interface port
Aluminum Interface port
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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

An update on the new fusor; just completed machine work on the surplus flange for the electrode assembly so it can mate with the fusor chamber. Getting surplus flanges saves a great deal of money but often means one needs to add bolt holes, threaded holes and/or new O-rings slots. Being able to machine such pieces is often necessary to get them to properly fit the existing hardware. Of course, not having access to proper machine tools nor the skill means farming it out (which can still save money depending on the level of work needed.)

Working stainless steel is not too difficult if one is experienced with cutting aluminum; it is important to set the cutting/drilling speed to very slow, uses machine cutting oil (generous) and one proceeds slowly in cutting or threading. Setting max depth on the drilling process/rig is essential - the quickest way to ruin a vacuum plate is cut all the way through when that side will be under vacuum and the other in air. Just a few tips on working steel and vacuum pieces.

In the previous post is a pic of the plate (with the O-ring) that will be bolted to this plate using the four new threaded holes. The O-ring on that other plate will go inside of my new threaded holes on the plate but be on the outside of the numerous inner holes. I do not want to use that copper gasket knife edge system on this surplus flange.
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Properly locking down plate to be centered and drilled
Properly locking down plate to be centered and drilled
Drilling hole in the plate
Drilling hole in the plate
Cutting thread for hole
Cutting thread for hole
Checking threaded hole with a bolt
Checking threaded hole with a bolt
Finished flange with four new threaded access holes (3/8 inch)
Finished flange with four new threaded access holes (3/8 inch)
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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

Well, quick test yesterday and out gassing for the system is severe and likely, a minor leak around the new electrode. My large two stage pump can only get the system down to 80 or 90 microns; the turbo just 5 microns.

So a clean up, rework the electrode seal, bake out and hopefully, the system can then get low enough to test for real leaks via dust off with the ion gauge. Not surprised by this out gassing since between my system parts being in air for five years, using surplus stuff exposed to who knows what, and a new design/assembly for the electrode would certainly lead to these types of issues. I guess this work will be the name of the game for a while. A fusor needs to be clean and mid 10^-5 torr and for that chamber right now, and that value looks far away .

After a clean up and bake out, I'll also do a plasma ashing of the chamber - oxygen is already present and the fusor power supply can be run at lower voltage in the near torr range. That will provide a deep cleaning of any organics or volatiles in the chamber or on the electrode.
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Dennis P Brown
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Re: New Fusor: progress

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Started the "bake out" of the fusor system; I did the main 'cross' and now doing an end cap - one is already done (top) and doing the left. The right, bottom, and main connector tree below that also need to be done. Having only 12 feet of heating tape for this chamber makes the going slow. Again, one get's what one can surplus and I'm happy to have it and that it works. The vacuum has slightly improved - from 80 to 50 microns but that is mostly, I'd guess, due to pumping on the system. Till I try high vac again, only then will I really see if this piecemeal bake out helped.
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Left end cap on the main fusor chamber cross
Left end cap on the main fusor chamber cross
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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

After a few hours of baking out a number of sections of the chamber and connectors, the current pressure is about 30 microns (rather high for my two stage pump.) Running the turbo, this drops below 1 micron and the ion gauge says 0.2 microns before cutting out. Certainly a significant improvement but not there yet - as in able to perform a leak check using the ionization gauge.

This is likely out gassing but there could be a very minor leak(s) somewhere in the system. As many old hands know, leak checking and getting a system really clean are both difficult tasks that are part of any new fusor system minimum requirements before one can attempt fusion. I have not yet installed the electrode and will wait till tomorrow to see if that can be done successfully - keeping the system wit has few connected sub-systems is SOP for vacuum checking. If I have time tomorrow, and the electrode passes muster, I might strike a plasma to further clean the chamber.

Till then, can't really make any determinations on further procedures. I will back fill the system with dry air both to prevent the system from taking in moist air and to further aid in drying the interior walls.
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Dennis P Brown
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Re: New Fusor: progress

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I am at the worse stage of vacuum leak detection - far too low to be any real leak (easy to find/hear) but not low enough to use standard precision detection methods (that are easy/cheap.) I will continue to try baking but using the two stage pump is not as effective as the turbo; however, reluctant to use the turbo - that is a good bit of strain on the unit. Unfortunately, my surplus gauge systems don't cover the mid to low 10^-3 torr range.

The large chamber looks ultra clean but that doesn't mean there isn't extensive absorbed water in the wall surface's. I'm concerned for my steel fore-line: being a bellows it has massive area for its volume. Also, I avoided a turbo bake since I had decided to use it. So that, the ion gauge & its connector as well as the fore-line will get a bake out. Might install the electrode - if not significant leakage from that (still haven't checked it), could then strike a plasma to further clean the chamber.

New systems are always fun.
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Dennis P Brown
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Re: New Fusor: progress

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Well, baked out that lower section. Let it cool down and then back filled with dry air. I moved my TC gauge from near the chamber down to that lower section. Since the main gate valve is above the turbo I closed that and only pumped the lower section down - that is, the turbo, its connection system and lines, as well as the fore-line bellows. The fore pump took that immediately down to 2 microns in under a minute (the normal base pressure/speed of my fore pump.) So that section is certainly good and fairly clean including that steel bellows section. The full system (main gate valve open) pumped down to just under 25 microns (an improvement.)

I then decided to add my deuterium system to the upper section so I could also include that in my vacuum diagnostics and upon trying to pump this all down discovered that deuterium system had a major leak (a bad coupling - needed teflon tape.) I fixed that and the system again returned to under 25 microns. I am now baking the chamber out at my max temp for the tape. This system is certainly the issue and I will look at the out gassing problem in greater detail now that I eliminated the fore line system, turbo and its connector system/lines.

Vacuum diagnostics is a slow, tedious procedure. Doing it as a step by step process - eliminating sections to rule them in or out - is how larger systems must be done. Like ruling out the fore line and turbo system but then discovering the issue with my deuterium supply line/couplings. If that was a very minor issue (of course, it wasn't) it could easily be missed relative to other out gassing problems for the chamber. Instead, it was obvious but that isn't always the case. Isolating systems/subsystems and even just single parts/couplings is the way vacuum diagnostics is performed.

Again, for newbie's, an essential technique to learn and master before any fusor can be made to operate.
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Jim Kovalchick
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Re: New Fusor: progress

Post by Jim Kovalchick »

Dennis,
Nice progress and great reports.

Your leak doesn't seem that bad. I wonder if you would find it easier to go ahead with lighting plasma and using it to help you with the leak search. Some here have had luck spraying possible leak points with alcohol and watching for plasma changes. The plasma also helps to bake and clean a chamber.

Jim K
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Dennis P Brown
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Re: New Fusor: progress

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Thank you Jim. I feel that while my post is certainly overly wordy and 'old hat' to the pro's here, newbies should really get a chance to see, in detail, the trial and tribulations that checking a system involves as well as the logic and methodology. Details and photo's may help to give them an idea on the procedures.

The good news is the turbo got the system down to the mid 10^-4 torr so I could use the trusty "Dust Off" methodology. I discovered that only the top most flange was leaking - all the coupling gaskets, including all the main chamber flanges, appear tight and show no effect from the Dust Off spray (unlike the top flange that caused a sudden jump in the ion gauge reading.) After adding some extra washers and tighten the bolts, the system dropped down to the low 10^-4 torr.

This is great news cause all the other (and there are a lot) of coupling/O-ring seals and flanges are good for the low 10^-4 torr. Getting below that is really a matter of out gassing; between keeping at vacuum, baking, and when I can, running a plasma, this level should drop to the mid 10^-5 torr. More then enough (i.e. clean enough) to consider the system ready as a fusor. Deuterium in a fusor does not tolerate water vapor at all and contaminates are always a bad idea to have around. Fusion is difficult enough without those (and a FYI - professional fusion community did NOT realize that simple fact about contaminates till the 1990's! While they routinely achieved 10^-8 or better torr it wasn't till they added an active 'getter' system that fusion made huge steps in plasma stability. I'd say ridiculous but they were physicist ... ;) )

Well, enough history.

My next step, as Jim has suggested, is to install the electrode. While I can't strike a plasma yet (but will certainly do that in the near future) I do need to check its seal system for leakage as well. So, back to the turbo and dust off; that is, if I can again get below 10^-3 torr - a new addition could cause issues.
Attachments
Trusty 'Dust Off' the prime leak detector for intermediate vacuum testing
Trusty 'Dust Off' the prime leak detector for intermediate vacuum testing
Top most flange (small one with the extension) that was leaking; added washers and retighten
Top most flange (small one with the extension) that was leaking; added washers and retighten
Last edited by Dennis P Brown on Thu Dec 02, 2021 9:06 am, edited 1 time in total.
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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

Checked the O-ring assembly on that small, upper flange and it was useless - it had cracked and separated providing no seal. Amazing the system achieved 10^-4 torr. Replaced the O-ring and installed the electrode. The system is reaching a fairly steady 3.5* 10^-4 torr. For a semi-first vacuum level not bad at all considering how long these parts have been exposed to moist air. However, still a bit of a ways to go.

I will, if I have time, install a small cathode assembly on the end of my electrode so I can run a plasma at some point; the steel coil will act a lot like a 'getter' depositing a small amount of an active metal that will both form a seal on the chamber walls and chemically bond with some contaminates.

I include a pic of three very handy tools in any vacuum workers diagnostic tool kit: Dust Off, Alcohol (can improve an O-ring seal besides helping to detect a leak location), and heating tape to wrap various parts/components of a vacuum system to help remove adhering water on the walls.

I should add, those that use KF fittings for connectors should always have a few extra O-rings, and at least one end cap to remove a device or isolate a system for vacuum diagnostics. I used one extensively in this work.
Attachments
Upper electrode assembly
Upper electrode assembly
End of the electrode shaft: the bolt end has a thru-hole to both prevent a virtual leak and hold the cathode shaft in place
End of the electrode shaft: the bolt end has a thru-hole to both prevent a virtual leak and hold the cathode shaft in place
Vacuum diagnostic tools: (Left to right) Dust Off, Alcohol, Heat Tape
Vacuum diagnostic tools: (Left to right) Dust Off, Alcohol, Heat Tape
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Richard Hull
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Re: New Fusor: progress

Post by Richard Hull »

Good, step by step system assembly reports, with photos, are of interest to even the old boys here, but as noted really are a teaching moment for the newbies. Keep 'em comin'....

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: New Fusor: progress

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Thank you Richard; from someone with your level of experience I really appreciate that feedback!

Well, there was a micro-leak at the center core of the electrode (between the steel core and ceramic body) - I used some liquid vacuum seal and baked it an hour at 300 C. Did the trick. My system (fore pump only) went from 70 microns to 4.5 microns! So, I'm very pleased with that pressure and that's w/o the turbo, of course.

I added an extra external ground box and used that to provide an independent star grounding for the chamber, power supply and key devices - with these voltages (and currents) one can't be too careful. Note I keep the HV cable well away from all metal parts, other wires, and vacuum system components. Cable insulation can fail and its also best not to test their capabilities.

With the system properly sealed, I ran the power to the electrode to use the trace air to create a plasma - the oxygen will further clean up the main chamber. The chamber (sealed off using the gate valve) climbs about 15 microns per minute from all sources(considering the large surface area, I am pleased with that rate.)

With that plasma run I now have "first" light; through, not yet with deuterium. But still a nice milestone in that I achieved routine fusor pressure levels with a plasma running.

Adding deuterium gas for a real run (the system is installed, though) will wait till I build a proper shielding system (not depending on the steel walls, that's for sure) and get my He-3 detector working (obviously, will require neutrons to really test). Those projects are now first up in the 'Q' and I hope to complete them in the near future. Then I will also try my new scintillation neutron detector and see if I can fire up my old Russian BF-3 tube (however, its operating voltage might be too high for my systems.) So when I get the He-3 detector up and running with a computer I will be ready to try some real fusion.

Still some minor odds and ends to finish on the vacuum system: run turbo for ultimate vacuum level check (at least 10^-5 torr), test my main gate valve for fine vacuum adjustment capabilities, add a mirror to indirectly see inside the chamber (need to avoid those x-rays), and adjust some equipment locations.

Bottom-line: As any experienced fusor knows, getting one's vacuum system up to speed is an absolute first required step before any fusion can be attempted - all else has to wait till that is functioning properly.

Aside: Newbies do note that if you want to get into the plasma club its important to demonstrate progress by giving some details of construction. This should also be done besides reporting plasma parameters - see my plasma photo with appropriate parameters cited as a possible example to follow. This furthers both your proof of your claim but also gets you noticed as a contributor. Furthermore, it makes getting to the ultimate goal - Neutron Club* - more likely (showing your path there.) Besides, this is what makes being a member of the forum fun!

Some plasma details for Newbie's: notice in the plasma picture the diffuse glow filling the entire field of view (chamber) - this shows that the plasma is really operating under 30 microns. The color is indicative of nitrogen gas (dominate ion emission.)

* Or attempt what I'm now trying to do - get on the list for successful nuclear activation via neutrons. In practice, getting neutrons first is the normal methodology but certainly one could do both simultaneously - demonstrate neutron detection via activation. But most of us first got in the neutron club using the normal method - demonstrated detection of neutrons using one of the proven detector methodologies.
Attachments
Lowest system pressure just with my fore pump running
Lowest system pressure just with my fore pump running
Chamber hooked up to my 32 kV, 38 ma power supply
Chamber hooked up to my 32 kV, 38 ma power supply
Air based electric plasma in chamber (can see faint hints of star mode; 8 kV, 28 ma, 12 microns pressure)
Air based electric plasma in chamber (can see faint hints of star mode; 8 kV, 28 ma, 12 microns pressure)
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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

Decided to get an early start on finishing various tasks on the fusor before I can attempt ...well... fusion.

Installed all shielding. To get sufficient shielding coverage, I'm going with two systems: an inner shield based on tiles for a close to the fusor chamber in order to create a maximum shadow effect; and a vertically mounted outer shield (fully painted & framed, lead sheet) to provide better operator coverage (offset vertically and horizontally relative to the cathode for better operator protection). A side mirror (angled) to view the cathode/plasma - to the right of the fusor. I include a pic of the cathode as viewed by the operator.

Aside: I have a calibrated 'dosimeter' to wear and an X-ray/gamma scintillation detector to provide radiation measurements for shielding performance.

I tested the 'ultimate' vacuum level (after just ten minutes of high vac pumping) and it got into the low 10^-5 torr; more then sufficient to assume the fusor is 'clean' before addition of deuterium gas.

My two neutron detector systems: a fast neutron sensitive PMT assembly (home made) and a counter/power supply for it; and my CHM-32 3He detector with its power/pre-amp & computer interface box. I put the CHM-32 in its moderator container - yes, could be bigger but I also have a large paraffin block to add.

So, I need to mount these detectors, test them with all electronics running along with a plasma (no deuterium) to get a noise baseline. Then the really challenging task of using deuterium gas, control the gate valve/system pressure/feed rate and variac, while simultaneously trying to get the voltage to its upper range without over driving the x-former. Fun (not) stuff before I can hope to get any real neutron measurements.

Only then can I attempt Ag and maybe In activation (?). If I had realized I needed a moderator for the Ag foil the first time I tried this effort I could have done this experiment years ago with my first successful fusor. Well, now I have the chance for the 'fun' of firing this fusor up with all new parameters to master. Really a lot of parts and effort to get this experiment back up - I forgot just how involved getting a complete fusor up and running is - especially the issue of creating a stable plasma; and this time, my effort was 'simpler' because I have a turn key 3He detector system rather then the complete 'make your own' BF-3 detector system (where some parts need a lot of assembly! Not unlike Ikea ... ;) )

I'll mount the PMT detector mid level just in front of the tile shielding (to decrease x-ray issues for the PMT. See pic.) I'll mount the moderator tube, extra paraffin block & 3He detector almost against the rear of the chamber in line (horizontally) behind the fusor - again, see pic. Once I establish a baseline neutron measurement, I will convert that moderator tube into my "neutron oven". That is, I will place a Geiger tube wrapped in Ag foil in that moderator tube and measure 'gamma counts' in real time the moment I extinguish the plasma/power. Hopefully that will enable me to measure/record an activation decay curve.

My original and known BF-3 detector is not really viable this time around since its operating voltage is too high for my counter black box and I am not building another system again for that detector ... or hope I don't!
Attachments
Fast Neutron PMT and location
Fast Neutron PMT and location
3He Detector support and Moderators
3He Detector support and Moderators
Complete system w/shielding and operator position (In my mini-research building I posted about in an earlier thread)
Complete system w/shielding and operator position (In my mini-research building I posted about in an earlier thread)
Cathode Image in operator's mirror (Aux ground box in background image; those are just extra grounding wires)
Cathode Image in operator's mirror (Aux ground box in background image; those are just extra grounding wires)
Fast base pressure for the fusor system
Fast base pressure for the fusor system
The Fast Neutron PMT detector system & counter/power
The Fast Neutron PMT detector system & counter/power
The 3He detector system, black box and software thumb drive
The 3He detector system, black box and software thumb drive
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Richard Hull
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Re: New Fusor: progress

Post by Richard Hull »

Nice setup and the turnkey neutron detection system will be a winner for sure.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: New Fusor: progress

Post by Dennis P Brown »

Hello every one; well I ran the fusor with deuterium and managed to get a stable plasma. Confused because it is operating below 1 micron to get over 20 kV. Never had that occur with my first fusor.

Tried running the PMT neutron detector - appeared to work or at least behave like it did - no counts with voltage below 15 kV; got a number of counts when over 20 kV; when I dialed back to 15 kV, the counts stopped and then started up as I ran to 20 kV. Got a lot faster when I was up near 27 kV; however, the counts where still lower than I liked so I decided to try various PMT voltages. In the higher range. That is when I started to have issues with the counter box/display and can't figure out what the problem is - appears to be having trouble again. Hope the voltage cut off diode did not fail again.

Decided this required another time to diagnose so I decided to run the 3He detector.

Of course the software for that device which worked perfectly yesterday (after I downloaded what I thought was a update fix as described on their site) now does not work at all today - refuses to load and offers no error. Some days one wonders about software and windows - both tend to be virus's that are meant to drive one to distraction. Of course windows changes their product and that ensures older software does not run. Companies supposedly supply fixes but it takes tricks to get their fixes to work - they forget to explain this since they don't have time to post these issues on their web site. See this far too often.

Well, at least the fusor ran in a stable manner but I am very confused with the fact that to get above 8 kV (@ 12 microns), my vacuum gauges (both!) indicate I'm below one micron - that makes little to no sense. However, I could easily control the current and voltage via the gate valve (normal) and use that to get any desired voltage (again, normal.) This was done while a controlled leak of deuterium being feed into the system.

Well, sent off an email and hope to get feed back on their software issue. Again, lack of information/instructions besides "load this" is not to me all that useful for a site to provide. I think they assume we are all administrators and experts in windows.

So much for a "Turn key" system; with windows, the concept of a turn key system is not what that term use to mean.
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Re: New Fusor: progress

Post by Richard Hull »

This is why I tend to go and build all electronics from scratch. You learn as you go, experiment as you go and if you need or desire software control, you grab an Arduino and program and debug it yourself. if you build and program something from scratch you can fix, modify, repair, reprogram and maintain it for as long as you find your build working to your desire.

As Dennis notes, you are at the mercy of the original manufacturer to cover all updates and changes by Microsoft with new software. I have had this issue in the past and have several PC's that are not on line that used to be online and down loaded good software that operated my OEM stuff in the past. They still do, with no issues. One is Win 98, two are XP and two are Windows 7. They will never go on line ever again. They are my main work computers and are isolated from Internet nasties and worthless updates.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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