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.
User avatar
Dennis P Brown
Posts: 1786
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: TMP Diagnosis

Post by Dennis P Brown » Tue Aug 15, 2017 12:00 pm

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.

User avatar
Rich Feldman
Posts: 1289
Joined: Mon Dec 21, 2009 11:59 pm
Real name: Rich Feldman
Location: Santa Clara County, CA, USA

Re: TMP Diagnosis

Post by Rich Feldman » Tue Aug 15, 2017 3:07 pm

>> 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 4:41 pm, edited 1 time in total.
All models are wrong; some models are useful. -- George Box

User avatar
Nick Peskosky
Posts: 135
Joined: Thu Aug 09, 2012 1:02 am
Real name: Nicholas Peskosky
Location: San Diego, CA

Re: TMP Diagnosis

Post by Nick Peskosky » Tue Aug 15, 2017 3:47 pm


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!
Nick Peskosky

"The whole of science is nothing more than the refinement of everyday thinking." - Albert Einstein

Jackson Oswalt
Posts: 98
Joined: Thu Jul 13, 2017 1:10 pm
Real name: Jackson Oswalt

Re: TMP Diagnosis

Post by Jackson Oswalt » Wed Aug 16, 2017 9:13 pm


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!
Youngest person to build a Fusor at 12 yrs

John Futter
Posts: 1587
Joined: Thu Apr 22, 2004 2:29 am
Real name: John Futter

Re: TMP Diagnosis

Post by John Futter » Thu Aug 17, 2017 2:17 am

Forget the ion pump
they need 10 to the -4 millibar to start about twice as good a vacuum that your robinair can do

User avatar
Richard Hull
Posts: 12091
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: TMP Diagnosis

Post by Richard Hull » Thu Aug 17, 2017 4:17 am

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

Johan Reinink
Posts: 14
Joined: Thu Nov 17, 2016 12:43 pm
Real name: Johan Reinink
Location: Enschede, The Netherlands

Re: TMP Diagnosis

Post by Johan Reinink » Thu Aug 17, 2017 12:33 pm

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:
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
Posts: 98
Joined: Thu Jul 13, 2017 1:10 pm
Real name: Jackson Oswalt

Re: TMP Diagnosis

Post by Jackson Oswalt » Thu Aug 17, 2017 9:39 pm

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.
Youngest person to build a Fusor at 12 yrs

User avatar
Dennis P Brown
Posts: 1786
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: TMP Diagnosis

Post by Dennis P Brown » Fri Aug 18, 2017 1:57 pm

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
Posts: 285
Joined: Thu Apr 17, 2014 4:43 pm
Real name: David Kunkle

Re: TMP Diagnosis

Post by David Kunkle » Fri Aug 18, 2017 3:58 pm

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.

Ernest Rutherford

Post Reply