Aqua Lung DX question

[Scotty]

I own a nice DX-Overpressure Breathing that I would very much like to return to service. Cosmetically, I'd give it a "B plus" - the unit is complete, minus the original bit for the metal mouthpiece (I understand OEM replacements are near impossible to find). The Lp diaphragm is shot - hard as a rock, brittle, but similar in style to ones I've seen pulled out of early DA's. I have not opened this regulator, my reasoning being that if replacement diaphragms or other parts are not available, why tear it apart and risk ruining a very nice display piece ( I seriously doubt this unit was ever opened before). Just need to know if it would be worth my while to send it out for restoration. I e-mailed someone about servicing/restoring it awhile back, but can't remember who it was. Any help/advice appreciated.

Oh yeah, anticipating the "are you sure it hasn't been modified to a Mistral" question, yes, I'm sure. It's all DX.

[SeaRat]

Scotty,

If it is a DX Overpressure Breathing regulator, then returning it to service presents only two main problems, the hoses and the yolk. You can easily replace the diaphragm with any made for either a Mistral or Aquamaster (same size, just the tabs haven't been folded up). The regulator itself has a small hose inside that probably ought to be replaced also. It is made of rubber, and has probably deteriorated badly. But the basic regulator is simply the early Mistral, with the hose-within-a-hose venturi. This is actually the most effective venturi ever developed, and the quietest-breathing regulator. I cannot tell you what to do with yours, but I can tell you what I did with mine.

--Replaced the hoses with new hoses (1" openings on both ends). I got mine from a safety supply house that sells replacement parts for self-contained breathing apparatus (firefighter SCBAs). These hoses are somewhat longer than normal ones, and therefore work much better for positioning the regulator low on my back.
--Simply put a new mouthpiece on the metal mouthpiece assembly.
--Decided not to replace the non-return valve on the inhalation side; I have never felt the need for it.
--Chromed the boxes (the bottom box, with the name plate, was chromed, and not covered, so if I would do it again I would make sure to retain the original paint for the label).
--Replaced the yolk with a long yolk that can handle a banjo fitting.
--Replaced the inner hose with a vinyl equivalent (available at aquarium supply houses).
--Replaced the sintered filter, and ensured that the mechanism is clean.
--I was able to put a clamp ring on my DX, so I didn't have to bother with the clips.

This regulator is simple to work on and maintain. The innerds are the same as the Mistral or DY or Jet Air, which means only six moving parts. Here's a couple of photos of my DX Overpressure Breathing regulator, with me (in not so good a pose) too.

And here's the tank/regulator setup I have with my DX:

I prefer this regulator for my close up and macro underwater photography, as it is quiet and it has hoses long enough that I can get the regulator completely behind me, out of sight of small fishes.

Once you make the modifications, be sure to make the mouthpiece seal properly, and that it is not torn; hoses too. If water gets into the mouthpiece of this regulator, it gets into the small venturi tube too. Because there are three small holes that the air comes out of, and fast, there will be a spray of water droplets coming straight into your mouth. It is uncomfortable, as I found out when I dove with a mouthpiece with a small tear in it.


Good luck,

John

[Scotty]

John, thanx a bunch 4 the info. I do have an extra Mistral diaphragm that I can swap out. I guess my next question would be about lever height after I change out the diaphragm - did you find you needed to make any adjustments after retrofitting? And if so, did you find any significant difference in performance?

Hoses are not a problem. This came to me with heavy-duty spiral-type hoses, same as those on my early model Heathways SCUBA regulator, only yellow. I somehow doubt they are the original hoses for this regulator, but they're in great shape, match the name plate, and are plenty long enough to allow freedom of motion. I've had them off and found the venturi hose and mouthpiece non-return valve to be in excellent condition as well. How all this stuff still looks new while the lp diaphagm had petrified is beyond me (I have a Navy-Type DA with the same problem).

-Scotty

[RMannix]

Preserve and store those yellow hoses, use replacement hoses to dive with.
Or sell the yellow hoses to buy a new car.

[SeaRat]

Scotty,

It sounds like you're almost ready to dive the DX! That's great. Be sure to keep the washer with the two "C" openings in place between the mouthpiece assembly and the inner hose. This acts to limit the amount of air coming into the mouthpiece system, and dampen the venturi (which can be quite strong without this washer). It had (has?) a unique non-return valve with two small attachment points to the washer. I have found the non-return not to be of much use, although if you still have it and it's still good, probably keep it.

Concerning the hoses, according to Fred Roberts in Basic Scuba, the original hoses tasted awful (medicine-like), and were changed out by most of the users of the DX very quickly. I still have mine, which are quite short but made so well it is possible they will never wear out (their about 1/8 inch thick rubber, even in the convolutions). I found them too short for good use, which is why I changed mine out. I would dive the healthways hoses, as I like the higher-visibility hoses.

The levers can be set the way the factory likes it, at the top of the box, but I like mine as far up as the new diaphragm will allow without causing a leak (flow) when assembled. This gives the best performance.

Good luck, and tell us how it goes.

John

[Scotty]

John, that would accurately describe the hoses on my Navy-type DA: Stiff, short, and thick, with 1" openings on both ends (this reg also has a metal mouthpiece tee, but without the DX's venturi tube/non return valve - has anyone else come across this model with a metal tee?) As for the yellow hoses on my DX, bagging 'em up for storage is without question. They're just way too nice and I know I'll never find another pair like them. I will retain the original yoke however, as I'm not a big fan of banjo adaptors. IMHO, they add an additional failure point at a critical connection for your air supply. I own one and used it once with my RAM about fifteen years ago, now it just hangs on my pegboard. Something about a thin O-ring that seals a high pressure component attached to a hose that gets moved about during the course of a dive made me a tad nervous. I realize that vintage divers salivate over getting their hands on these and many use them regularly, but personally I've just never been sold on the whole "banjo adaptor" concept. For me, vintage diving is minimalist diving and minimalist diving means not having to worry about little pieces parts between me and my air supply.

Thanx again for all of your help!

[SeaRat]

Scotty,

The real reason for the change in the yolk is simply to get it to fit "modern" (post 1954) valve bodies. The old one will only fit a few valves currently available, one of which is the USD double tank manifold (which it does fit).

Good luck,

John

[Scotty]

Okay, well then, the yoke on this DX must have been changed out before I got it. I do know which style yoke you're talking about, though - one of my Broxton units has this style yoke (a rough forged-looking thing) and, yes, it doesn't accept much in the way of tank valves. I'm glad I'm getting a chance to discuss all this because the DX is still relatively new to me, being that I never had the chance to examine one other than mine.

-Scotty