Is there anything wrong with this vacuum pump?

[Alexander Ziemecki]

Hello all. I am about to buy a pump, but am getting a red flag from the seller. He says that it is very good condition -"vintage"- but that he has not tested it due to no skill or tools to do so. Is there anything immediately wrong with it from these pictures? I don't have the skill to know yet, either.

Thanks for your time.

[Richard Hull]

This is a secondary diffusion pump, of course. We assume you already have the fore pump, (mechanical pump).

Externally, it looks really good. The jet stack, (christmas tree) also is very clean. The real issue is the heater good? To test this an ohmmeter needs to be placed across the two electrical pins as the base and should not read "open" there should be some low resistance there.
Typically the heaters can be easily replaced. However, a heater for this model might not be available any more. With a bad heater, and no replacement available, it is a fine museum piece example of a non-functional, older "diff" pump.

Richard Hull

[Alexander Ziemecki]

Hello Richard, thanks for your reply and instructions! I have gone ahead and bought it and will reply in this thread how it functions when it gets here, in about a week. Glad to hear it looks really good, because I was planning on building my own from scrap until I came across this for incredibly cheap. Still looking for a cheap-enough-good-enough roughing pump. Figured the diffusion pump was a bigger problem to solve first.

I think I will probably be able to hack together my own heater for this if it does not work, but do you agree? Very little of my education ever touched on vacuum systems or low-pressure physics, and what little I did hear was mostly anecdotes from professors explaining why they stopped being experimentalists ("as I watched all of our precious hydrogen bubble away through the skin of the chamber itself, i felt my heart sink and for the first time considered turning to a life of crime" etc).

[Arya Afshari]

Hi Alexander,

I'm also in the market for a diffusion pump. The one I'm looking at is from ebay with a similar exhaust port (see below). Do you know how the connection is made to that sort of straight pipe since there's no KF flange nor Conflat flange?

Thanks,
- Arya

[Rich Gorski]

Arya,

I'm assuming your asking about the large flat plate with the four bolts. This appears to be an ASA flange (American Standard Association). These are o-ring sealed flanges.

Your can find much info out there on this type of HV connection. Try Kurt J. Lester for more info.

https://www.lesker.com/newweb/flanges/f ... _asa_1.cfm

Rich G.

[Arya Afshari]

Hi Rich,

I appreciate the reply. I was actually referring to the exhaust port where the foreline pump connects.

Thanks,
- Arya

[Rich Gorski]

OK, that is either a simple flexible greased hose connection with hose clamp (nothing wrong with that at forepump pressure. Vacuum level will get down to 10 microns with a tight fit of the hose to pipe end) or it was a soldered connection to something else. My guess it was a flexible hose connected there.

Rich

[Arya Afshari]

Thank Rich! I also thought a flexible tube could be slid on there but wasn't sure if the foreline pump would still be able to pull a vacuum without a KF flange or Conflat flange.

- Arya