How to change vacuum tubes on the VPI 16.5 ?

It's simply a friction fit. Just pull it out firmly, jigglingly as needed to pull it loose. It is not fragile. Easiest to do if you pull out the tower the tube is mounted in so you can get a firm grip.
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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

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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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.

OK, I have a 16.5 and I also misunderstood the headline. I started thinking an EL-34 might be about the right size, then . . .

Serious advice on removal will not be repeated here. However, one caution is to adjust the replacement suction tube so that the vacuum slot is at the 185 degrees position when viewed from the outer end, not straight down (180 degrees). Also, the velvet pad should not extend more than 1/16" beyond the record. Otherwise, you will not achieve proper vacuum. It really is not difficult and should take only a few minutes.

Replacing it is easy. Rebiasing it is hard.

Thanks guys for all your help !

I had the switches cryo treated and my 16.5 works better then ever!

Hello Studio68, if you change tubes often you may want to get the whole assembly, including the black insert piece. Some folks change the tubes for dirtier/ cleaner albums. The old tube can be used for very dirty Lps and the newer for cleaner Lps.

I bought a second tube holder (the black plastic thing referred to above) so I can easily change tubes for the 2 step Audio Intelligent fluids. They suggest 2 tubes and 2 brushed to avoid contamination of the different types of fluid, 1 being enzymatic and 2 removing the enzyme fluid. They even have a step 3 that is just pure water, but that is too many steps for me and may not yield and better results.

Experiment with the pure water rinse step before deciding not to use it. Makes a big difference here to use that ultra pure water rinse step, but I'm using Walker Audio Prelude so there may be a difference.
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Emaailsts,
I think you forgot one step, the Archivist Formula! :-)
I just bought the whole kit from Jim at AIVS.

Doug D might chime in here soon, but from what I understand from him, each following step compliments, and further enhances the previous steps.

From my understanding, the second step contains some alcohol, and completely removes any trace of the first step Enzymatic Formula.

Then the Archivist Formula will continue on, and remove any traces of alcohol, and since the alcohol only remains on the LP for such a very short time, no harm is caused to the LP in this process.

Lastly, comes the purified water, which will completer the cleaning job, and you good to go.

Yes, I do know it sounds like a bunch of extra work, as I've yet to experience this myself, and this is sure considerable light years away from the old fashioned "Discwasher" we all used in the olden days.

I see this as detailing a car. So many "one Step" Wax Products are available on the market, but when one wishes to get the very best results, with no compromise, one will have to resort to specialized products, (Washing, Clay Bars, Glazes, Polishes, Sealers) and taking very similar "steps" to achieve the very best results.

I'm going to keep reminding, and saying to myself as I'm sweating over my cherished LPs, that, "It's worth the effort, your LPs are gonna sound awesome!"! Mark