How to change vacuum tubes on the VPI 16.5 ?

Do you have to twist the tube then pull out? Or just a straight pull out is fine?

Straight pull should work. Be aware of a lockiing pin that may be there to keep for tube from twisting, but will not affect a straight pull.
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Steady the black metal hub it plugs into with one hand and withdraw the plastic tube with the other. It's quite easy as long as you pull in the direction of the tube's long axis - don't apply any sideways or lifting force. You need to take it off now and then to clean the velvet and check its condition.

Of course, I DID misunderstand the title of your post when I first saw it and looked out of sheer curiosity!

Chris

Are you replacing it with NOS tubes?

Does it clean better with NOS tubes? would be my second question....

Finally have you tried rolling other tubes?

Drmoss, For a second I misunderstood the title too and I have a 16.5!

Studio68, Since your question has been answered, permission to have a little fun as Cytocycle has begun?

I changed the tube on mine and now it sucks more than ever.