A Bunch of Failures

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Jackson Oswalt
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A Bunch of Failures

Post by Jackson Oswalt » Fri Dec 22, 2017 4:14 am

Hello all!

Today I attempted a test in which I pumped my system down for approx. 25 minutes with simply a roughing pump (a bad one at that) and then used my 50kv spellman power supply to ignite the plasma. The results were frustrating to say the least. I was planning to turn on my diff. Pump for the first time, but do to the fact my TC gauge apparently doesn't work I didn't know if I was reaching the correct pressures. Most disappointing of all, when I did turn on the supply, I got the most depressing little sparkle at the base of a grid. Mind you, I can usually cover the entire grid with plasma just with an oil burner transformer and Variac combo. I'll start with the supply. The supply is the same of that in the "Christmas Comes Early" post from a while back, which can be found here: viewtopic.php?f=11&t=11477. It's a Spellman PTV50N200. Generally, it's rated at 4ma, but following the rather misleading guide in the above post I upgraded it to 7ma (350 watts)... I think. That's the very problem. I have no way of testing it. Without a proper meter, I can't measure it and am in no place to spend any $$$ on a meter. So, I tried to go off what other people had done that had worked and had been tested, but that didn't get me very far. All I know is that it outputs something, but as soon as I put that output on the grid it barely outputs anything. So if anybody is experienced with such supplies, I'd appreciate if you try your hand at solving this apparent mystery. I replaced C39 and R50, as it says to do in the post above, but didn't change R23. That's because the only info on what to change R23 for is for the 504 watt version, not the 350w version. Today I purchased some 50kohm potentiometers for the upgraded supply instead of the recommended 20kohm pots, which was recommended in the post. We'll see if they improve anything. Now onto the gauge. What could be the deal here? In a previous post I've mentioned it, but nothing has seemed to make work. It's Consolidated, both the gauge and meter (the meter is battery operated). If I fiddle with it for some time, I can get it to show a little less than atmosphere, but surely that can't be the true pressure after a half hour of pumping. I'm happy to answer any questions and any suggestions are appreciated.

Thanks!

Items Mentioned:
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Entire Setup
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C39 and R50 (Replacements)
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Complete Innards of Supply
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Supply Wiring System (Potentiometers)
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Supply Info
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TC Meter
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TC Tube
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Dennis P Brown
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Re: A Bunch of Failures

Post by Dennis P Brown » Fri Dec 22, 2017 1:37 pm

First off, without knowing your vacuum you are in the dark for many issues. That issue must be addressed first or you will not even strike a proper plasma and testing your mods on the supply will prove fruitless.

That you say: " I can usually cover the entire grid with plasma just with an oil burner transformer and Variac combo." This isn't good and tells me your system isn't even close to getting much under a few hundred microns or possibly even torr(s). The entire space in your chamber should glow brightly below 50 microns when even an oil burner voltage (3-5 kV!) is applied. Definitely, you have vacuum issues.

The standard question is what does the vacuum gauge read when you just pump on the detector part of the vacuum gauge? That is, fully isolated what vacuum does the pump pull? If that does not get below 50 or so microns something is very wrong - either the gauge system (detector and/or readout unit) or the pump. If you have a pump issue you are dead in the water and must address that; gauge issues are easier in being far less costly to deal with.

Your system using KF seals (unless something is seriously amiss) should allow even a cheap pump to easily pull below a torr. Of course, the vast majority of cheap TC detectors can't measure that high a vacuum. So, either buy a cheap mechanical dial gauge that can easily handle that range or (better) try and get a working micron gauge unit from somewhere else (I was able to borrow) a known calibrated unit if you know anyone that has a vacuum system.

If you have a public university/community college nearby, simply call the physics department, explain to a Prof what you are doing (they will be interested as long as you are professional in your request) and that you need to test your vacuum gauge because it isn't maybe correct (not borrow one!) They will very likely let you come in and test your unit against their know equipment (really.) I've done that.

Once you confirm your gauge's operation you should be able to address your vacuum capabilities and then, test your power supply properly using a plasma.

An aside: I have tested MANY old TC heads/detectors and 75% or more leaked terribly. Some I re-sealed successfully by adding a vacuum sealing liquid into them by drilling a hole in the base (electrode side.) Most of these tries did not work. Also, only the exact detector unit designed for the reader will work - most TC detector units are, of course, wrong and useless for a given model of gauge reader. You MUST have the correct TC unit; rarely but it happens, the cable can be an issue. Do ohm the leads (check the TC pins, too.) This requires you have the schematics for the unit.

There is no easy solution for a unknown vacuum gauge except have a second unit on hand that is know to be good.

Hopefully, someone can weigh in on the power supply issue. I will add that your power supply should not be able to strike a proper plasma unless your pressure is low enough so don't yet doubt your PS! First, get a proper vacuum before deciding your power supply isn't working properly.
Last edited by Dennis P Brown on Sat Dec 23, 2017 2:00 pm, edited 1 time in total.

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Richard Hull
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Re: A Bunch of Failures

Post by Richard Hull » Fri Dec 22, 2017 4:22 pm

Dennis said it. Vacuum is it. As he said, disconnect the mechanical pump from the system. Attach the TC gauge to the inlet of the pump and report what the gauge reads. Do this and only this and get back to us with a report.

That Robinair pump looks new. Robinair is a good name in the refrigeration biz and should, if purchased new, dip under 30 microns at the head.

I hope you know that the volume of the line from the pump to your chamber is almost the same volume as the chamber. Kind of unusual, but it should work fine with a good pump. I can barely see a tiny brass adapter at the pump joined to the large line.... Kind of a choke point. When you get the gauge hooked to the pump and report the vacuum level, photograph that simple set up for us, please.

I assume the mountain of "step down cones" lead to your deuterium gas inlet?? I also assume your HV insulator is out of view on the other side of the fusor chamber cross??

The 004 tube is a CVC tube that is very common and well known. The readout is another matter. It is not CVC but does have the requisite 55 ohm movement for most all TC gauge tubes. I assume you purchased the readout and tube together in one buy? I assume you hit the "set point" mark using the pot on the controller before operating it. (calibrated the meter to the tube) So very much is at issue here related to vacuum alone.

Solve this vacuum issue first...Forget the supply. The supply will be a whole other can of worms.

Richard Hull
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Fusion is the energy of the future....and it always will be
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Silviu Tamasdan
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Re: A Bunch of Failures

Post by Silviu Tamasdan » Fri Dec 22, 2017 5:43 pm

...and when you do get to testing the power supply, I suggest building a power load like I'm planning on in this thread: viewtopic.php?f=11&t=11985&start=10#p78361

50 of the 100kohm/10W resistors in series will allow you to test the supply at 50kV and up to 10mA. I paid less than $30 for 100 of these: https://www.ebay.com/itm/5-Pcs-Axial-Ce ... 2749.l2649
And about $35 including shipping for 100 resistors of 20kohm/20W https://www.aliexpress.com/item/SQP-20W ... 0.0.xPJ7WT
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Jackson Oswalt
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Re: A Bunch of Failures

Post by Jackson Oswalt » Sun Dec 31, 2017 9:34 pm

A few days ago I received my 4th TC gauge. None have worked so far. I attach it to my system and find my pressure is 15000 microns after 45 minutes of pumping it down. Next I attach it direct;y to the head of the pump and find the same thing. I then clean it out and do the same thing. The gauge reads 9300 microns. Oddly, when I press on the cable it either jumps back up or goes down to 8300. I then clean it out once more and get down to 8900 microns without applying any pressure to the cable. Remember, I run my pump for 30mins for every test, so surely it would get farther than 8900 microns. Should I pursue a replacement sensor? The gauge is a Yellow Jacket 69086.
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Tom McCarthy
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Re: A Bunch of Failures

Post by Tom McCarthy » Sun Dec 31, 2017 9:46 pm

How do you know that all of the previous gauges were/are broken?

Jackson Oswalt
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Re: A Bunch of Failures

Post by Jackson Oswalt » Sun Dec 31, 2017 10:18 pm

The first arrived without it's front panel, for which I received a refund. The second meter wouldn't provide power to the tube and third wouldn't display anything other than atmospheric pressure despite long pump downs.
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Richard Hull
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Re: A Bunch of Failures

Post by Richard Hull » Sun Dec 31, 2017 10:40 pm

I have never seen any TC gauge using the 004 tube with a meter capable of reading a pressure of 15 torr! (15000 microns.) However, it seems you have one with a super crowded scale. There is something grossly wrong here. Either the pump is worthless or the gauge not functioning as it should. You need to determine which it is. A small plasma test is in order now. The glow discharge should tell it all.

You seem to have gone about all of this in a wrong manner. For now, consider the 50KV supply worthless. Never use it again, until you have full control of your vacuum. You need a bit more reliable high voltage supply of no more than 5-10kv powered by a variac. A neon transformer and HV rectifier would do.

Use no gauges...hook the mechanical pump only to the fusor and fusor chamber to the lower voltage supply and see what you discharge looks like. Then we can tell whether it is the pump or massive leaks. Get rid of all the vacuum system!! pump to fusor then better 10kv supply to the fusor and report back. This whole thread is running a loop-dee-loop and going no where.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Jackson Oswalt
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Re: A Bunch of Failures

Post by Jackson Oswalt » Sun Dec 31, 2017 10:45 pm

I presume 004 tube is the type of tube the Yellow Jacket 69086 has. It reads up to 25 torr.
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Richard Hull
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Re: A Bunch of Failures

Post by Richard Hull » Sun Dec 31, 2017 11:07 pm

If you have this gauge and it is new and the tube matches the gauge and you calibrated it. It is probably as good as gold. Your pump is crap which is difficult to believe, it looks new. A good two stage Robinair should hit 20 microns at the head inlet, easy.

Before you pump does the gauge read atmosphere and drop as you pump works? (this is at the inlet not in the vacuum system) How long does it take to hit the lowest rather stable pressure from turn on>

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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