Chuck Sherwood wrote:
All the broken pumps I've seen were neglected and ruined on the pump side,


What are the important clues to look for when buying a used pump?

Here are a few things to look for. Some of these you can only check if
you can see the pump in person, but that's always a good idea if it's
nearby.

* Check out the general physical condition: does the pump appear to have
been looked after well or is it knocked around and covered with grime
and rust?

* Ask the seller what is has been used for. If it has been used in
industry for neon sign manufacture or air conditioning servicing it will
probably have seen much heavier use that if it was used in a school
science laboratory.

* If the seller has a vacuum gauge available, ask them to measure the
pump's ultimate vacuum.

* Inspect the oil. Is it dirty? Metallic particles in the oil may
indicate heavy pump wear. Vacuum pump oil is usually colourless and
doesn't smell. If it smells it's the wrong kind of oil.

* Unscrew the oil drain and let a few drops run out. Is the oil
contaminated with water?

* Listen to the pump running. These pumps are usually pretty quiet.
Clacking noises may indicate sticking vanes.

It seems from what Harry says that you should be fine with a mechanical
pump for making neon signs, although you will need to be able to
manufacture and seal the glassware. Perhaps Harry could confirm if a
single stage pump is adequate or if a two stage pump is required?

Hope this helps

Chris