Noisy Edwards EXT250 Pump

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David Kunkle
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Noisy Edwards EXT250 Pump

Post by David Kunkle » Fri Sep 23, 2016 7:00 pm

This Edwards EXT250 is my 2nd turbo pump. Noticed yesterday it's making a high pitched whine even after it's up to speed. Not real loud, but noticeable that it wasn't there before- slightly annoying pitch. Still pumps down easily into the E-6's Torr like before. Other than the noise, all seems OK. I don't have a manual for this. Wondering if it could need grease? Or is it on its way to becoming another doorstop?

After the first one blew up and I tried to replace the bearings twice without success, I picked this model because it's a lot newer and plentiful on ebay. If anything went wrong, I'd just grab another one and slap it in place with the old cable and controller instead of having to weld in new flanges, etc. But now that push may be coming to shove, the thought of another $800 doesn't sound so appealing.

Dan Knapp
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Re: Noisy Edwards EXT250 Pump

Post by Dan Knapp » Fri Sep 23, 2016 11:02 pm

A singing turbo is a prodrome to bearing failure The safest thing to do is replace the bearings before they fail.
Some bearing failures are catastrophic.

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Re: Noisy Edwards EXT250 Pump

Post by prestonbarrows » Sat Sep 24, 2016 2:44 am

That high pitched whine is almost always the bearings starting to wear out. This happens due to physical shocks to the unit while running, high gas loads, or just long service life. If a turbo sits unused on a shelf for a long period, the bearings can also degrade. If you read the manual for most turbos, the recommended time between servicing is surprising short. Keep an eye on it to make sure it does not get progressively worse. If you can monitor the power draw on your turbo controller, that will also give a qualitative measure of it's health. A good turbo should only draw 10-20W when properly blanked off. If it is more like 100's of Watts, it is probably nearing the end of it's life.

The only real option to fix the situation is to send the unit in to the manufacturer for a rebuild. Expect to pay about 20-50% of the price of a brand new unit for that service. This is on the order of a few grand.

Generally, the bigger the turbo, the bigger this issue is and the faster it creeps up. 50 l/s mini turbos can be abused to hell and keep on running at reduced performance without catastrophic failure. The EXT250 is a mid size and can probably keep trucking along for a good while still but expect it to only get worse over time. At that size, it may not crash, but will draw more and more power and give lower and lower pressures. Any turbo you find second hand will almost certainly have been used long enough to be nearing its service date or have some other flaw; that is why they are selling it for cheap.

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Rich Feldman
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Re: Noisy Edwards EXT250 Pump

Post by Rich Feldman » Sat Sep 24, 2016 5:40 am

>> A good turbo should only draw 10-20W when properly blanked off. If it is more like 100's of Watts, it is probably nearing the end of it's life.

If the extra power draw is due to bearing drag, then those extra watts must be turning into heat at the bearing(s). No wonder that phase of the life cycle is short.
Richard Feldman

Jerry Biehler
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Re: Noisy Edwards EXT250 Pump

Post by Jerry Biehler » Sat Sep 24, 2016 6:52 pm

Alpine bearing sells Turbo bearings, they have them for a lot of models, probably have one for yours. The prices are not bad.

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Re: Noisy Edwards EXT250 Pump

Post by David Kunkle » Sun Sep 25, 2016 11:20 pm

Thanks for all the info, guys. I've got Alpine's site pulled up, but have no idea what bearings it takes- not in the manual. Hopefully they could tell me if I called.

Found turbovacuum.com. Only place I found that has a rebuild kit for this pump- $685. Have to talk to them first, but I'd assume it would include instructions? Might be worth it at that rate- can't find any youtube vids specifically for this pump either.

Found an unused rebuilt EXT250 by a pump company for $1800 obo on ebay. At least it's probably done right and ready to go.
3 ways I could probably go at this point. Need more info to decide.

Manual states inlet end is supported by a "frictionless magnetic bearing". Is that the same as a mag-lev? Didn't think this model was one of those.

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Dennis P Brown
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Re: Noisy Edwards EXT250 Pump

Post by Dennis P Brown » Mon Sep 26, 2016 10:43 am

Rebuilding a turbo isn't a slam-dunk; removing and replacing bearing(s) can be tricky. Also, removing blades isn't easy nor always simple - order can matter a great deal on some pumps (that is blades are not all the same) so keep that in mind if you disassemble a turbo. A mistake and the turbo might end up as junk and the cost of the kit is then "thrown away".

Buying a rebuild is straight forward but pricey as you see but at least it has a decent service life.

A diffusion pump is also a very inexpensive way to go and costs a small fraction of even a rebuild kit.

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Re: Noisy Edwards EXT250 Pump

Post by Jerry Biehler » Tue Sep 27, 2016 2:20 am

No, not the same as mag-lev, it is a similar setup to what pfeiffer uses where they have permanent magnets at the top of the rotor and inside the spider on the housing. The magnets support the rotor.

The pfeiffers are pretty easy to replace bearings, the bearing is accessible from the bottom and since there is only one bearing, its pretty fast.

David Kunkle
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Re: Noisy Edwards EXT250 Pump

Post by David Kunkle » Wed Sep 28, 2016 1:44 am

Dennis P Brown wrote:Rebuilding a turbo isn't a slam-dunk; removing and replacing bearing(s) can be tricky. Also, removing blades isn't easy nor always simple - order can matter a great deal on some pumps (that is blades are not all the same) so keep that in mind if you disassemble a turbo. A mistake and the turbo might end up as junk and the cost of the kit is then "thrown away".

Buying a rebuild is straight forward but pricey as you see but at least it has a decent service life.

A diffusion pump is also a very inexpensive way to go and costs a small fraction of even a rebuild kit.
Tried to fix the first one with new bearings twice- didn't go well. Failed both times and cost over $400 for 2 sets of bearings. But, it was very old and difficult to determine with confidence exactly what the correct bearings were. I know how tricky it can get. Sending this latest Edwards in for a rebuild would be in the thousands- out of the question. Cheaper to snag a fresh, newly rebuilt one off ebay.

Haven't had a chance to call on just getting bearings or the rebuild kit.

Knowing what I know now, if I had to do it over, I'd probably start with a diff pump. Since I already have the cables, controller, setup , etc. for this turbo, I'm still bent on getting a working turbo instead of my grenade to be that I have now.
Last edited by David Kunkle on Wed Sep 28, 2016 1:48 am, edited 1 time in total.

David Kunkle
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Re: Noisy Edwards EXT250 Pump

Post by David Kunkle » Wed Sep 28, 2016 1:47 am

Jerry Biehler wrote:No, not the same as mag-lev, it is a similar setup to what pfeiffer uses where they have permanent magnets at the top of the rotor and inside the spider on the housing. The magnets support the rotor.

The pfeiffers are pretty easy to replace bearings, the bearing is accessible from the bottom and since there is only one bearing, its pretty fast.
Hadn't thought to ask if any turbos were easier to repair if the worst happens again. Don't suppose there's any chance my Edwards controller and cable would work on a similar model Pfeiffer?

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