Inside the Tekna Regulator

[William Farrell]

Long ago I was at a Northern CA scuba shop looking at Tekna regulators. I asked the sales guy if I could service it myself. "No way," he said, "it's extremely complicated and you'd probably mis-adjust it and die."

Well, some years later I decided to find out. I've been buying used Teknas on eBay for the past several months and restoring them---when possible. The design is quite unique.

The valve bodies came in brass and plastic. People tend to look down on the plastic ones and I don't know why---they're lighter, will never corrode, and have exactly the same insides. Here's one of each:

Let's take the brass one apart:

And take off the circlip:

Remove the rubber spacer:

Two holes on the top and a bolt on the bottom:

With a socket on the bolt and needlenose pliers in the holes, we can take it apart:

And here's the innards:

Bolt on the left, strong spring to keep things together, tiny spring to keep the needle poppet square on its seat. Looking inside the housing we can see the seat:

And finally the poppet. I don't know what else to call it. It's a miniscule rubber donut on the needle that doesn't lift straight off the seat but rather tilts off when you create a vacuum by inhaling:

This one is in good shape, as were about 50% of the dozen or so I worked on. Here's one that's not so good (I pulled this one off the needle):

An interesting system---very little that can go wrong, and zero possibility of adjustment. It either works or it doesn't. I've tried replacing the degraded rubber donuts with all sorts of stuff---o rings, teflon, gaskets, etc.---but I haven't found the magic material yet. Some are too hard: the poppet won't seal on the seat and the regulator free flows. Some are too soft: the regulator holds pressure, but it takes too much effort to tilt the poppet off the soft seat to start airflow. I'll find it eventually.

So there you have it, the inside story on a long-forgotten technical marvel. Hope you enjoyed it.

 

[Nemrod]

I bought my first Tekna in 1978, I think it was from Kenlee's in Houston, used them until the mid 90s when parts dried up. Though I do have some parts, I have given most of my stash away and the last little bit is my reserve as I still use them occasionally, maybe.

The plastic unit (on the right) you have is the T2100BX. They were, may I say, crap. Much detuned and tended to crack. I would not waste my time on a T2100BX. The previous plastic housing with the brass mechanism body are fine, that is the T2100B and I much prefer the all metal T2100. The BX as I said was detuned to attempt to prevent shallow water stutter or feedback.

The pilot servo tilt valve seal goes bad and causes a continuous leak/freeflow. The main flow valve, they tend to get hard or take a seat and then once moved may refuse to ever seal again, thus again causing a constant flow of air.

The Tekna is effectively a downstream design despite having an upstream tilt pilot valve. Over pressure will offset the main flow valve and bleed pressure off. This photo is not too old, probably the last time I pulled the old T2100 out:

I took mine to 238 feet, just saying.

I have never found a way to replace/renew the tilt valve seat or to fabricate a serviceable main flow valve. I used B2 Proseal to make a few pours into the tilt valve cup, I have also tried urethane with limited success. Frankly, as much as I enjoyed mine, there are other opportunities out there to play with old regulators given that Teknas were always rare, there simply are so few about, well, kind of an odd bird.

The second stage was intended to never need service.

N

 

[William Farrell]

I'm curious about a couple of things in your response: (1) how are these "detuned"? (2) what is the "main flow valve"?

As I said, I've had a dozen of these completely apart, and there is no "tuning" possible on any of them, plastic or brass valve body, plastic or brass housing. Further, there's no "main flow valve" that I can detect, certainly nothing that can take a seat. The needle with poppet IS the valve that controls air flow.

If you have photos that show what you're saying, that would be great.

 

[Nemrod]

They were factory detuned to reduce stutter. The valve body cracks, which is why they added the metal ring, not a good fix.

The main flow valve is what I call that quarter size plastic diaphragm with the little hole in the middle. The tilt valves offsets dropping pressure in the pilot chamber which causes that main valve to lift off the body (with all of those little holes in it) and allow IP air to flow. Once disturbed, by disassembly, getting the valve to find home (on all of those little holes) is nigh impossible.

The tilt valve initiates flow, it is a pneumatic servo valve. The main air flow comes through the back of the body through the holes.

N

 

[William Farrell]

Got it. Here's a pic of the main valve parts---metal cover, rubber(ish) seat, and metal body with holes:

I turned the seat upside down to show if it had taken a set---it hasn't, and it breathed the same after reassembly as before. I'll be checking my others now.

I sure would like to know what material they used for that tilt valve seat. Not that I'm planning to re-introduce Tekna to the world of scuba, it's just a challenge.

 

[Nemrod]

What surprises people is that there is no direct mechanical connection from the ambient diaphragm to the valve with servo assisted second stages. It is pneumatic assisted/amplified. That tilt servo assist valve requires only a tiny force to off seat thus the tiny ambient diaphragm, no direct connection to the main flow valve mechanism, pneumatic only. When you hear people say the Tekna is an upstream design this is the part they are missing, only the servo tilt valve is upstream.

To resurface the tilt valve, using urethane or possible silicone rubber, mix the material. Clean the valve seat completely. Dip an then twirl the little valve in the material and then remove it and allow to set. Then using a single edge razor blade cut the material flush to the face by spinning the seat to the blade. Be careful not to score the lever rod. Then remove the remaining material. Now you have a new seat.

I once considered making a few of these Tekna-ish servo second stages but thought better of it. It would cost a small fortune. I would replace that main flow diagram valve with a piston. This would result in the unit being somewhat larger and heavier. I would also incorporate a spring with a shallow/deep switch to counter balance the piston main valve to eliminate shallow water stutter. A rotating vane partially obstructing the mouthpiece outlet might accomplish the same thing with less complexity.

N

 

[William Farrell]

Thanks for the tip, I'll try some urethane. I've been taking solid stuff like teflon, cutting it to size with a hole punch, then drilling it for the needle. As I said, it ends up being too soft or too hard. I even tried cutting out some Scubapro and Conshelf seats to fit---again, too soft or too hard. Did you ever get get one of these DIY seats to work?

 

[Nemrod]

Thanks for the tip, I'll try some urethane. I've been taking solid stuff like teflon, cutting it to size with a hole punch, then drilling it for the needle. As I said, it ends up being too soft or too hard. I even tried cutting out some Scubapro and Conshelf seats to fit---again, too soft or too hard. Did you ever get get one of these DIY seats to work?

Yes, but not perfectly, I lost interest. The T2100 in the photo above has a urethane DIY seat. I am sure I could figure out something if I kept at it.

Another tip, double hose regulators of all types are much more fun and satisfying. And even better, somebody else has invested in the effort to make all sorts of cool parts for them and practically gives them away . This leaves me copious amounts of time to loiter on SB and restore English 3-speeds and build telescopes and blow stuff up (mostly accidentally).

N

 

[William Farrell]

Double hose sounds like fun. My wife won't be happy though..........

 

[Fibonacci]

I was clearing an old computer HDD and discovered some rendering tests of a 3D model of my Tekna 2100B I made as part of a Uni CAD project 'back in the day' .

I always liked the Tekna's ease of breathing, even at 52m on the President Coolidge and revolutionary side vent design... never had a problem with reliability, just ran out of service parts.

Anyway just thought I'd share with other Tekna 2100 fans