Fusor Forums

My luck at buying pumps is bad. Wanted a decent backing pump and found a E2M12 locally. Seller said, "Like new vacuum pump in good working order." When I picked it up I noticed some brown residue in the exhaust port. Seller seems like a decent guy. I asked him how it had been used and he said for vacuum epoxy molding or something like that. Alarm rang in my head but I took it anyway hoping for the best.

Today I put a gauge directly on the input and measured 15 Torr (not millitorr!). Maybe something wrong with my gauge. Put it on an old refrigeration service pump I have and measured 16 microns. Another symptom is if I open the ballast I don't hear much change in the pumping sound. (Not sure if that means anything.) So the pump is crap right now.

A couple years ago I bought a "good" pump that was similarly abused. I intended to do a full rebuild so invested extra $ on the kit. When I got inside and cleaned the horror of deposits for several days I eventually found pump shaft and internals scored. Total loss unless all the expensive parts replaced.

My instinct is to try to return this Edwards for full refund and begin search again. If I can get most of my money back and keep it, does anyone think it is worth looking inside, or just walk away?

If the "old refrigeration pump" isn't yours make an offer now! 16 microns ain't bad and is likely to be better than most any used pump you will find, ever.

Richard Hull

The refrigeration pump was a used eBay purchase. It's a Yellow Jacket 6 CFM and shows external signs that it was used a while. That was a decent buy. Working pretty good now but I'm not sure how it will hold up if I run it many hours continuous. I've heard these types of pumps wear out pretty fast and can overheat if run many hours.

The gauge I used is an MKS 325 Moducell Pirani sensor. I'm not sure if it's dead accurate but should be pretty close. It is spec'ed for 1 millitorr to 100 torr. Its output is not linear. I use the manufacturers voltage to pressure table to convert from my volt meter to vacuum.

I've had my feelers out for a while looking for a suitable name brand pump but my best instincts so far have only found junk in my several-hundred-dollar price range. Starting to think I may have to break down and go for an expensive rebuilt pump from a vacuum company with a warranty.

My eBay-foo seemed to be good a few years ago but lately I've had a number of bad experiences.

I have two yellow jacket 6 CFM pumps and they are superb. I did my very first fusion using the yellow jacket and a lesker micromaze trap. The lowest I ever got the yellow jacket by itself was about 10 microns with fresh oil, but it would yank down my fusor II to 20 microns in under 2 minutes. With the Yellow jacket and the micromaze, (after a bake out), fusor III would go sub micron. I found it to be the best direct drive I ever owned and it beat out my Edwards direct drive pro pump! Since 2003 I have only used belt drive, slow winder Welch pumps. They are the best in the world, provided you find a good one.

Richard Hull

A vacuum of 15 torr means something isn't working - an internal valve is always open, or part of the inter workings have come lose/off; most likely needs to be disassembled, all parts given a good cleaning, and maybe it will work well again if the former. Maybe the repair is easy - maybe. Taking it apart may damage gaskets (likely with an old pump) - in which case they'd need to replace or if not too bad, repaired ... still, unless you can return the pump, you have little to lose by disassembly. Maybe something came apart that is easy to fix ...but if you damage the gasket(s), return might not be allowed. Unless a very low price (parts for future similar pump?), return first seems the best choice.

Richard,
Thanks for the positive words about the Yellow Jackets. That's good encouragement to use the one I have.

Dennis,
I guess I was hoping someone would have some magic to try. I'm going to see if I can cancel the purchase and return the Edwards pump. It's definitely not worth the money I paid.

Make sure to use super nice, clean oil in the yellow jacket and change it after a few hours of run time to make sure you are now running as clean as possible and have rid the pump of the garbage of its former life. However, with 16 microns showing, it sounds like you might have already taken care of that chore.

Richard Hull

I would take it apart and order a rebuild kit from duniway stockroom.

rexa wrote:My luck at buying pumps is bad. Wanted a decent backing pump and found a E2M12 locally. Seller said, "Like new vacuum pump in good working order." When I picked it up I noticed some brown residue in the exhaust port. Seller seems like a decent guy. I asked him how it had been used and he said for vacuum epoxy molding or something like that. Alarm rang in my head but I took it anyway hoping for the best.

Today I put a gauge directly on the input and measured 15 Torr (not millitorr!). Maybe something wrong with my gauge. Put it on an old refrigeration service pump I have and measured 16 microns. Another symptom is if I open the ballast I don't hear much change in the pumping sound. (Not sure if that means anything.) So the pump is crap right now.

A couple years ago I bought a "good" pump that was similarly abused. I intended to do a full rebuild so invested extra $ on the kit. When I got inside and cleaned the horror of deposits for several days I eventually found pump shaft and internals scored. Total loss unless all the expensive parts replaced.

My instinct is to try to return this Edwards for full refund and begin search again. If I can get most of my money back and keep it, does anyone think it is worth looking inside, or just walk away?

is this pressure with the oil it came with or after several cleaning cycles?
I bought a completely seized leybold that had been submerged at some time from the tide mark inside the motor casing!
After dismantling and cleaning then rebuilding 5 microns

The assumption is that the Yellow Jacket at 16 microns was used and no more money poured into the very dead Edwards which could be rebuilt at leisure at some future date or that he tried to get his money back, (probably the best route).

16 microns is a fabulous forepump pressure and will serve well with a Diff pump. Paying good money to do better would be a throw away of good cash needed for other stuff.

Richard