Vintage Double Hose

I just bought a Aqua Lung DA Aquamaster. I plan on sending it in to have it serviced. I was told that you have to use 2250 PSI or less tanks.

Thank You
Joseph

There options for rebuilding. You can add a Phoenix nozzle assy and that would allow you to have 3 hi and 3 low pressure ports. Or just a great Bryan rebuild with a new seat should allow 3000 psi diving.

There are two issues WRT working press for the Aquamaster, yoke type and intermediate pressure setting. The old DA's from 1950's and early 60's used a short yoke which is rather weak. It will withstand 3000 psi but has enough stretch that it could cause some types of O ring to pinch or leak. Yes, O rings have evolved along with valve type. The "long" yoke is somewhat stronger. The other issue is ease of breathing. Being unbalanced, the intermediate pressure decreases as tank press increases resulting in hard breathing at high tank press. Some divers have adjusted the IP to a higher average level to compensate. A newer development is the VDH "Phoenix" module which replaces the first stage. The included yoke is rated 4000 psi (by me, LOL). Seriously, the Phoenix is very strong. Moreover, this device is balanced. It requires professional guidance to install. One drawback, as this causes the regulator to offset forward somewhat it may present difficulties when using a vintage strap arrangement. Some backpacks, like the old Scubapro from early 70's are a perfect fit, however.

pescador775 wrote: The other issue is ease of breathing. Being unbalanced, the intermediate pressure decreases as tank press increases resulting in hard breathing at high tank press. Some divers have adjusted the IP to a higher average level to compensate.

Actually the IP pressure is at it's highest point at low cylinder pressure on an unbalanced 1st stage. That's why it's best to adjust the IP at 300-500 psi on them. Perhaps you are thinking of downstream vis upstream 2nd stages?

Some backpacks, like the old Scubapro from early 70's are a perfect fit, however.

Unfortunately there is more to having a backpack fit, so to speak. The position of the regulator on the diver's back is very iimportant. The three photos I have attached show you how the reg should be positioned and how it should not. (2 of the 3 are right and one is wrong.) The Phoenix is used in all of the pictures. The length of the Phoenix is not really an issue if you use the right harness system:

Example A

Example B

Example C


The correct positon is seen in A and C. In example B the reg is way too high which gives poor breathing characteristics and a pain in the back of the head. Unfortunately, I haven't found a plastic or metal molded backpac of the 1970's or 1980's that, if worn properly with the "meaty" part of the pack in the small of the back as intended, allows for correct regulator position. Actually, a modern BC (did I actually say that) allows for better reg position than the molded packs of the 60s-80s.
Allan

Bryan wrote:

pescador775 wrote: The other issue is ease of breathing. Being unbalanced, the intermediate pressure decreases as tank press increases resulting in hard breathing at high tank press. Some divers have adjusted the IP to a higher average level to compensate.

Actually the IP pressure is at it's highest point at low cylinder pressure on an unbalanced 1st stage. That's why it's best to adjust the IP at 300-500 psi on them. Perhaps you are thinking of downstream vis upstream 2nd stages?

I think you guys are saying the same thing, but backwards to each other. I did have to read Pescador statement several times, but I think you are both saying the same thing.

Edit: What I mean is that you are coming at it from the opposite perspective. Those that make sense?

The Navy did use the DA Aqua Master with their 3000 psi tanks for a long time.

Be aware that the Navy did have plenty of spare first stage seat at that time. The higher pressure will add some wear at the seat, but I don't know how significant.


IMHO what Pescador is saying about the yoke is a valid point, but I don't think it is a show stopper. I have seen pictures of the short yokes on old Navy twin 3000 psi cylinders.

The gent want'd to know if the 2250 limitation was valid. I explained that the the old yokes were iffy and the DA would breath hard with a 3000 psi tank. Seems plain enough.

I also alluded, but did not spell out, the objection to the Phoenix's additional stand off. This can have the effect of digging the regulator body into the divers back. Some backpacks like the old Healthways and Scubapro will work. The reason has to do with the short stature of these packs and also related to the thickness of the pack. The short, thick pack allows better placement of the Phoenix as opposed to newer packs with a handle which will interfere with the Phoenix . The extra thickness of any pack as opposed to a harness will prevent the regulator body from pressing on the diver's back or neck. This has little or nothing to do with "correct placement". These issues cannot be finessed by fiddling with adjustments.

joeyhugz wrote:I just bought a Aqua Lung DA Aquamaster. I plan on sending it in to have it serviced. I was told that you have to use 2250 PSI or less tanks.

Thank You
Joseph

Hi Joseph, after I sent my DA to Bryan I have had no problem using 3000 psi tanks with a banjo. However I can't wait to get my Phoenix! Here's a link to some dive pix from today using the AL 80...

http://www.flickr.com/photos/88052882@N00/

Poog