TMP Diagnosis

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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Richard Hull
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Re: TMP Diagnosis

Post by Richard Hull »

Turbos, especially used and second hand ones, purchased "at range", can be nothing but a pain. This is why a "no moving parts" diff pump starts off with a big advantage. Even a diff pump demands a good heater and a clean stack or you are back to more issues, still minor, compared to major turbo issues.

I have owned a perfectly functional 3" throat turbo with all cables and controller for 2 years, but will not install it as my diff pump is "plumbed in" and has worked well for 12 years in my fusor IV.
"If it ain't broke don't fix it" and "let a sleeping dog lie".

The real issue with any secondary high vacuum pump is size. Turbos are typically just the right size, (small). Diff pump offerings can be very inexpensive, but are often large, ( 4" throat or larger). These large diff pumps should be avoided.

No secondary pump should have a throat of 4-inches or larger. Plumbing adaptations on these larger offerings can be complex and costly if one is not a good machinist.

Good luck on getting the turbo to spin up

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
Roberto Ferrari
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Re: TMP Diagnosis

Post by Roberto Ferrari »

Adding to Richard’s wise words, I would comment on Diff pump sources.
Of course eBay is a must but keep an eye to damaged or scrapped Mass Spectrometers.
From 20 years now it is common in those systems to use small diff pumps, air cooled, of small size.
Service people following employer policy replace all the pump. So search for damaged units at universities and labs.
Basic damage is heater cartridge burned off but most of them are replaceable. Some having a glass window can get a crack on it. Just take it off and weld a blank plate.
My small lab has 3 of those diff pumps on use and 3 more on the shelf, recovered from scrap.
Good luck!
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Richard Hull
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Re: TMP Diagnosis

Post by Richard Hull »

I will second Roberto's advice! Old, discarded, air cooled diff pumps off mass specs and helium leak detectors are ideal for the fusor builder. This are typically 2" throated pumps, but 3" is also common.

If you go turbo you need to be very careful in any purchase effort.

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
Jackson Oswalt
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Re: TMP Diagnosis

Post by Jackson Oswalt »

David,

Your guess is as good as mine when it comes to the brand. There's is no doubt in my mind that Rigaku had some part in the pump. It's branded as "Rigaku" everywhere I look, so my guess they had some sort of deal with Varian that ended quite some time ago. The pump is from 1995.

As for the oil spillage, yes, it was in the vacuum inlet as well as outlet (because that's where it spilled out of). Fortunately, I've seen a few companies that could clean/repair the pump if needed, though I am trying to avoid that. I'm sure the price would be in the thousands.

Until I'm certain that the turbo is busted, I'm going to stick with it. Despite it's issues, I still believe it was a steal.

Thanks for the responses everybody. It's been a big help!
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David Kunkle
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Re: TMP Diagnosis

Post by David Kunkle »

If oil was coming out the inlet port that connects to your vacuum chamber, I have little doubt that oil is covering your rotors and the rest of your insides, and that is your entire problem. Not quite sure how oil spilled out and "soaked" it. The oil is probably causing a lot of drag making it stumble when it tries to spin up.

And, yeah, sending a turbo in to a company is a minimum of $1500 to $2k and up. I've attempted to repair the same turbo twice with failure, while I know some here have seemingly repaired theirs successfully. Not sure how many would admit if it blew up after some too short a time period. ;) I've been known to go back to ebay and buy another used one that was compatible with the controllers I already had.

$160 is definitely a good deal........ on a good, working turbo. Apparently it was in good running order when the guy sold it to you. If you got it back in February, it's probably too long ago to complain that it was defective or packed improperly for shipping- but you could always give it a shot.
If your experiment needs statistics, you ought to have done a better experiment.

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Jackson Oswalt
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Re: TMP Diagnosis

Post by Jackson Oswalt »

Thanks for the help. I just have one question: Isn't the oil supposed to be on the rotors so it doesn't wear down? Or is it only in the motor? Second, although I'm sure the oil is a major problem, I still bet that the cruddy vacuum is also a suspect. Again, thanks for the help. I'll look into cleaning the pump and with any luck it will be fixed.
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David Kunkle
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Re: TMP Diagnosis

Post by David Kunkle »

No, the oil or grease is only supposed to be on the upper and lower bearings that support the rotor shaft. This keeps the bearings from wearing down- not the rotor. The rotors' only job is to spin quietly in a vacuum- they never actually touch anything.
If your experiment needs statistics, you ought to have done a better experiment.

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Jerry Biehler
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Re: TMP Diagnosis

Post by Jerry Biehler »

Its probably not the oil. This pump is probably not a turbo-drag so it is going to need probably 50-100mtorr on the foreline for it to be happy.
Johan Reinink
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Re: TMP Diagnosis

Post by Johan Reinink »

Even in a terrible vacuum a turbo spins up to several thousand rpm, not really like "stumbling" described by OP. Usually controllers don't blow fuses, they just push on until either a timeout (some even skip this), overheating or normal operation.

How many pins does the connector to the turbo have? If you can find the winding connections (low ohmic, significant induction) you can check if all connections are equal to find a winding problem that could blow a fuse. Since the rotor spins well I'd suspect the controller. Also, that guy of the youtube video also has this video: https://www.youtube.com/watch?v=PjOTTGOunI4 I hope that's not your turbo!

The styling of the pump looks like a Seiko Seiki unit, I'm not surprised Rigaku doesn't know about this pump, it's not their market.
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Re: TMP Diagnosis

Post by John Futter »

Your robinair pump is not good enough!!!!!
The controllers ramp up at a set speed and if the foreline pressure is not good enough the controller senses this and will shut down or will blow a fuse due to excess current demand from a lagging rotor
You need to know that your foreline pressure is well below 1 x 10^1 millibar or 5x 10^-2 torr before attenpting to start one of these old pumps.
even if your robinair got to the approved vacuum the spinning pump would overcome it and stall on the resulting high foreline pressure

I see you still have not corrected your earlier photos and now probably can not
it has taken me a long time to spot the upside down robinair

Take the advice
get a diff pump learn how to use that with all the needed metrology (meters ie foreline and high vac)then try to apply it to your Turbo.
secondly most turbos do not like being in storage for very long as oil drys out in the wrong places.
some turbos have a repair program built in where they vary the speed and time to try to get the lubrication circulating properly before going to full speed
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Dennis P Brown
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Re: TMP Diagnosis

Post by Dennis P Brown »

I too got a working turbo, cable and controller for cheap ($10!) and it still works great after seven years. Pays to pay attention to junk being sold on ebay by companies that specialize in old/used gov/company surplus. That said, I use it only for a high vac system and not my fusor. My fusor uses a water cooled diffusion pump. That is easy to use, works great, never needs any real upkeep and came with a butterfly manual controlled gate valve/small chamber attached to it (has ports for vacuum gauges)- cost $110. Water systems are not liked by most people and are often a steal if one can deal with water. Bottom-line: Deals are there if one watches for them.

Cleaning the vans on a turbo isn't difficult but one has to be careful that they are not bent in the process; if that has already occurred then, yes, they can be straighten if bent (I've done this for a unit that was stopped by a bolt that fell into a running unit! It had numerous very badly bent vanes (no broken) and I fixed it and it runs perfectly now) but it requires patience and a bit of skill. If that is an issue, let me know and I can explain how to do it (but it is a dangerous process for the pump.)

The main rotor and vanes should spin (by hand) freely and there should be no sound of contact at all. If not, that must be corrected. Also, if the bearings are old/dragging then the unit will have issues (again, spinning it by hand should show this). Bad bearings will lead to a high current by the coils and this will either shut the unit down and/or blow a fuse (NEVER use a fuse greater than called for and NEVER replace a fuse more than once. That is just asking to burn out the coils or controller. Locate the issue and correct it.)

Some (esp. older units) turbo's allow the bearings to be re-oiled. Mine allows this and I have done it (required a few runs until the new oil out gassed.) The issue is the oil is very special (read expensive.) Turbos are nice for high vac but really are not needed for a fusor; yes, if one has one (and a gate valve) that will work well but a good DP has advantages and does NOT need to have a trap. I would never use my turbo for the fusor since the DP works so well.
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Rich Feldman
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Re: TMP Diagnosis

Post by Rich Feldman »

>> It just sorta stumbles. It tries to speed up, but then it stops.

>> Most turbos do not like being in storage for very long ... Some have a repair program built in where they vary the speed and time to try to get the lubrication circulating properly before going to full speed.


Hmm, maybe Jackson's controller picked up a Stuxnet infection.
Last edited by Rich Feldman on Tue Aug 15, 2017 12:41 pm, edited 1 time in total.
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Nick Peskosky
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Re: TMP Diagnosis

Post by Nick Peskosky »

Jackson,

If you are looking to make the leap into disassembling the TMP and cleaning it, I recommend you consult my older post on the ins-outs of this process: viewtopic.php?f=10&t=8602&p=59335&hilit ... rbo#p59335

If the turbo spins freely, my money is on the controller. Could you post pictures of the H-bridge circuitry? You may have a bad IGBT/FET pair or a hall effect sensor which is failing to pick up on the shaft rotation -> causing issues with proper sequencing of the phase rotation. Have you checked the output waveform of the PWM driver or the actual winding outputs? Misshapen waveforms at either or these debug points may indicate either a logic issue/timeout or a damaged solid-state switch. Shooting in the dark here... but hopefully this helps!
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Jackson Oswalt
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Re: TMP Diagnosis

Post by Jackson Oswalt »

Hello!

First off, I apologize by the delayed response. As some of you may know, school has started back, limiting my free time to about 2 hours a day. The sad part is it'll only get worse.

Second, thanks again for all the help. Previously I've only known a small amount about the possible issues, but now I'm pretty confident the problem isn't at all what I thought.

Third, Considering it would be rather time consuming to make a separate reply to every comment (I would If I could), I'm going to try to answer all of the replys made after my last post. I'm going to start with the oldest, then move up to the most recent.

1. Jerry, you're probably right. As far as I know, the Robinair pump might only be getting me down to 300-400 microns. I really need to get a working TC, but they're all $40+.
2. Johan, there's a good chance you're right as well. According to Gooferking Science, the guy who used to own the same turbo (but in working condition) said that there didn't need to be a vacuum for the turbo to start. Second, I've seen the video of explaining the dead turbo. However, he explained how it died. It was an unrelated cause. Third, the connector between the pump and controller isn't just a bunch of alligator clips. It's the one designed specifically for the TMP.
3. John, I know. The Robinair sucks. I'm looking into diffusion pumps, but it is it possible I can use an ion pump instead? I've heard good things.
4. Dennis, first, the top rotor does spin freely. I think. It has the sound of a bearing *whooshing* around and of course stops after a bit because it's not being turned via the motor. There's no obvious resistance, but I don't really have the knowledge to tell. Thanks for the advice on not burning the fuses out. Generally, I don't let the fuse blow, but when I see the TMP do the same old thing I shut it off.
5. Rich, ha.......ha........ha.
6. Nick, thanks for the offer, but I don't think I'm ready for that yet. As I said, I think it spins freely. As for the rest of your post, I can tell you've got some expertise. Unfortunately, I'm only in middle school and have practically no idea what you mean. XD. I don't own an oscilloscope either, but if you can dumb it down for me it would be much appreciated.

Thanks all!
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John Futter
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Re: TMP Diagnosis

Post by John Futter »

Jackson
Forget the ion pump
they need 10 to the -4 millibar to start about twice as good a vacuum that your robinair can do
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Richard Hull
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Re: TMP Diagnosis

Post by Richard Hull »

Ion pumps and Ti sub pumps have no place in a fusor vacuum steup.

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
Johan Reinink
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Re: TMP Diagnosis

Post by Johan Reinink »

Jackson, Getting a working pirani or TC gauge is very useful for vacuumwork, I can definitely recommend it.
Still I don't think a high foreline pressure is the problem. 400 micron is around 0.5mbar which terrible performance for a dual stage rotary vane vacuum pump but it's good enough to test a turbo. A pressure of 10^-2 to 10^-3 is recommended for turbo's without a molecular drag stage but the maximum they can take is a lot higher, usually 10^-1 to 5*10^-1 mbar depending on the pump. With a drag stage they allow up to 10mbar foreline pressure, again lower is recommended. In any case a turbo should rev up to a substantial fraction of it's operating speed if it's working properly.
... it doesn't go. It just sorta stumbles.
That tells me pressure is not the problem, even in air turbo's spin up to several thousand rpm.

How well does the rotor spin? Compare with this:
https://www.youtube.com/watch?v=T8jz1LNJ4L4
Hearing ANY bearing noise when spinning by hand is a very bad sign. Replacing a worn out bearing with a new one is about as costly as a proper functioning second hand turbo.

You're probably going to need electronic knowledge and tools, prepare to invest in things like an oscilloscope. For now a good multimeter would already bring you quite far. In any case this is possibly quite a project, so do it for the fun and learning, not to easily obtain a high vacuum.

Just count the pins of the connector of the turbo. 8 pins? Easy debugging, has 3 for windings and some things like monitoring temperature. Around 15~20 pins? Probably has hall sensors and other fun stuff, a bit more difficult to debug without a manual. A gazillion pins? It's a magnetically levitated pump.
Jackson Oswalt
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Re: TMP Diagnosis

Post by Jackson Oswalt »

The controller side of the cable has 10 pins, but the TMP side has 8 spaces. There are 8 pins on the actual pump.

When I spin the TMP by hand it spins for about 10 seconds, slows down, and comes to a halt. The whole time it makes. 'Whirring" noise. Let me know if I should upload a video.
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Dennis P Brown
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Re: TMP Diagnosis

Post by Dennis P Brown »

Since developing knowledge is a means in of itself, for someone with a good background in electronics, I'd say do all the diagnostics and learn all about the turbo for the fun. That appears not to be either your background nor what you are interested in; as such, there are always deals on diffusion pumps but beware - water cooled ones are cheaper (and often larger) and that means a lot of issues - getting water and drain lines to where you are working; larger flanges/adapters/gate valves which means far more costly unless one (like I) have access to a shop and can do a lot of rather advanced machine work with a lathe. Again, does not look like your preferred path.

All that is just to say, you might want to wait and watch ebay for a small air cooled unit to become available for a reasonable price - not likely but possible. That said, you will still need diffusion pump oil and that could exceed the cost of a diffusion pump.

Since you neither have a good two stage vacuum pump or a proper cheap thermo-couple grade vacuum gauge, these are, in my opinion critical first steps towards creating a useful vacuum system. And you should consider solving these issues first (while a fusor needs many support systems: deuterium gas, power supply, neutron detector system) the vacuum is the most important first support system and one that has the most uses for other projects if one does not do just a fusor. Also, critical for learning the real details (start, at least) of using any system that will support a plasma.

Of course, a pump and TC gauge system are useless unless one can connect the various components together; which means one must buy those connecting components (connecting flanges of some type, hoses of some type) once you have decided on how you want to go (Again, FAQ's under Vacuum.) But I feel KF is the best approach for any newbie with a limited budget and try to use 25 mm size (I use 25 mm all all my support systems except for my turbo inlet which is 15 mm (adapter used, of course).) Lots of both new (and cheap from china) and surplus KF stuff that can create a nice fore pump system for either a turbo or DP is available on ebay. Especially surplus stuff like steel bellow hoses can be a steal if one is careful (always have return option or don't buy - a leaking steel hose is just a boat anchor!)

Always check people here on high end items like DP's, two stage pumps, a specific power supply (but DO read the FAQ's on that critical topic) etc.

A real fusor uses a lot of complex, some very dangerous, and not easy to build support systems unless one can buy working turn key stuff (expensive.)

Good luck
David Kunkle
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Re: TMP Diagnosis

Post by David Kunkle »

I'll second what Dennis said about the 2 stage pump and need for a thermocouple gauge. At least the thermocouple first- that way you'll be able to see where you're at with the 2 stage pump. It is a "must have" if you intend to go any further.

You may as well post a video of spinning the turbine blades- as long as there's sound. ;) "Whirring" could be OK- or not. I've got my system apart lately for changes, and I just spun my turbo this a.m. to check it. Really no sound while it's spinning unless I get my ear less than a foot away- then I hear a little whirring like blades moving thru air/maybe it's bearings turning smoothly. Of course, I know my hearing isn't what it used to be either, so your mileage may vary. Took 12 to 15 secs to come to a stop.
If your experiment needs statistics, you ought to have done a better experiment.

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Aaron J Hardin
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Re: TMP Diagnosis

Post by Aaron J Hardin »

Considering that these pumps run between $400-$900 in good condition I would lean towards a faulty pump. The condition described is a shorted winding. Check that the wiring is correct as this will have similar symptoms as will water/condensation on your stator.

A bad hallefect sensor is a possibility, however this would not blow fuses (unless faulty wiring). It would likely overheat or indicate a fault.

The oil is not an issue, it is non conductive and will create minor drag. Once you repair the windings (or evaporate any water) run the pump on low rpm and purge with dry nitrogen. There is a sight glass at the bottom cap of these pumps, the oil should settle at the halfway point.

I know this is an older post but Molecular Turbopumps are vastly superior in many ways and worth the effort to get running correctly. Yes they are overkill for many hobbyists but to name a few benefits:
-They are especially useful in a fusor where the objective is to collide hydrogen^2 (explosive) into helium (also explosive)
-You can control the vacuum speed 100:1 in many applications
-They can operate for extended periods of time uninterrupted
and finally, the cleanliness
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Re: TMP Diagnosis

Post by John Futter »

Aaron
what?????
a lot of RAP spelt with a "C"
Helium is one of the noble gasses
Most turbos are on the second hand market because their bearings are past end of life.
In 40 failures in our lab of turbos all except one was bearing failure.
the odd one out was vane failure (read spectacular) a mass of scrap aluminium

Any water vapor would mean that you do not have sufficient vacuum for backing and the pump should not be started.

For fusor work for inexperienced vacuum practitioners I would recommend Diff pumps - less of a mess when making mistakes this applies to the $$$ spent as well

as an aside turbos do not like running at typical fusor vacuums ie on th edge of molecular flow where blade tip damge is foremost
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