Poseidon 3950 and 3960 differences + mating with Cyklon seconds

[mbussado]

Hello ScubaBoard forum - I just joined and for the life of me I don't know how I could do without you all for so long.

I have been maintaining my own several sets of 39X0 series of first stages (50's and 60's) for about 4 years as it is difficult to find techs in British Columbia or in the pacific islands where I go.

I wanted to ask an open question here... I noticed the only difference between the 3950 and 3960 is an additional O ring. I have also noticed that one of my 3950's has an additional smaller bias spring inside the larger one.

I have retrofitted O rings to all the 3950's years ago and have had more than 100 dives with this set up on air up to 100% O2 deco and at depths from shallow up to 110 meters.

I have tuned the IP on all of them to 9.5 Bars and have them matched to Cyklon second stages (1 metal body that is more than 20 years old and 3 plastic, black and yellow newer bodies) and a full face mask.

My question to any of you and to the venerable Jorgen Nillson are:
1) What other differences are there between the 3950/60?
2) What is the net effect of the second O ring aside for the higher working IP used with the Jetstream second stage, eg. are there any safety considerations in adding the O ring from the 3960 service kit to the 3950 first stage?
3) Is the configuration matching the 3950/60 to Cyklons and non poseidon second stage (part of a full face mask system) by setting the IP to 9.5 bar (the operating pressure of the full face mask) appropriate and safe?
4) Is it correct that the 2960 first stage HAS to have an over pressure valve in the LP hose as unlike the 3950/60 design it does not have an integral safety valve

I will never swap away from my Poseidon and have been using the equipment since day one.

Tack så mycke

Marco in Vancouver...

 

[Jorgen Nilsson]

Hi Marco!

Lets see if I can answer your questions:

• The only difference between a 3950 1st stage (it's actually a 3720 1st stage) and a 3960 1st stage (it's actually a 3790 1st stage), when it comes to parts, is the o-ring you mention. The 3960 1st stage must have the o-ring if a Jetstream 2nd stage is attached to it while the 3950 1st stage doesn't need it if there's a Cyklon 2nd stage attached to it.
• The additional o-ring used on a 3960 1st stage is there to maximize the air flow through the LP ports, as the Jetstream 2nd stage design require as much air flow as possible to seal. The Cyklon 2nd stage design do not require the same high air flow rate.
• Jetstream and Cyklon 2nd stages work at a very different intermediate pressure, so mixing these two 2nd stages on the same 1st stage, with an IP of 9,5 bar is NOT recommended. This could lead to one of the 2nd stage models failing. The Cyklon 2nd stage needs an intermediate pressure of 11,5 bar (167 psi) while the Jetstream 2nd stage needs an intermediate pressure of 8,5 bar (123 psi).
• When adding any non-Poseidon equipment to your Poseidon 1st stages, you need to make sure that the intermediate pressure these non-Poseidon components require, match the intermediate pressure that the Poseidon equipment uses. Using any breathing equipment, regardless of brand, at an intermediate pressure that is outside the manufacturer's specification, can lead to life threatening malfunctions.
• The old 2960 Jetstream 1st stage did not have a built in OPV. So to prevent the Jetstream 2nd stage from being damaged if the intermediate pressure would suddenly increase, the LP hose had a built in OPV. So the answer to your question is that if you are using a 1st stage from an 2960 Jetstream and you don't have an external OPV in one of the 1st stage LP ports, you MUST use a hose with a built in OPV.
• The reason why one of your 1st stages has two adjustment springs instead of just one, is simply because that is an old 1st stage. When that 1st stage was designed, we could not find a spring manufacturer that could make one spring strong enough, so we had to use two. In 1995, we did some upgrades to these 1st stages, among them the introduction of a single adjustment spring strong enough. If you have a 1st stage with two springs and you can get the desired intermediate pressure, you can continue using the two springs. If you can't get the desired intermediate pressure, the two springs are replaced with one spring.

I would also like to comment on your statement that you use your these regulators with both regular compressed air and 100% O2. This is NOT recommended, using these 1st stages with very high levels of O2. The reason for this is the lubricant used when these 1st stages were manufactured. For all non-Nitrox/non-O2 1st stages, we use a silicone based lubricant and this is pretty much impossible to wash away, to get a 1st stage O2 clean. Doing this can lead to a 1st stage oxygen burn, something we have seen evidence of in the past.
As far as we know, there's only one organization that can clean a 1st stage where a silicone based lubricant has been used, to make it O2 clean, and that is NASA.

Diver's safety is our prime concern thus it is very important that you let a trained service technician work on your equipment to ensure that they are set up/adjusted the way they are supposed to, to ensure functionality. I fully understand and respect that you have difficulties finding a Poseidon Service technician in your area, but I recommend that you check out our dealer location on our website (Poseidon) or get in touch with our representative in Canada (jack@poseidoncanada.ca) to track down a service center in your area that can assist you with your Poseidon equipment.


Med Vänliga Hälsningar

Jörgen Nilsson

 

[TONY CHANEY]

As a devoted Poseidon diver I just learned alot! I also have been using my Jetstreams and Cylons with 100% O2 for a long time. I am not that much into diving with 100% and like lower O2 mixes better for deco (50-87%) so with lower O2 mixes I will continue to use them. Mbussado you might want to shoot a PM to rsingler on this forum.

 

[mbussado]

Tack for svaret Jörgen,

I'd love to be your representative in western canada and get trained to service out here - I know the reason you don't sell a lot of equipment here is because most of the dive shops don't stock the products and talk them down citing poor servicing (and the other mythical conversation about up/downstream) aband incompatibility with DIR principles - which is nonsense because I could not think of any brand that takes so much advantage out of sheer (and proven) simplicity than Poseidon.

• I put the O rings in all the regs so I know they are all configured exactly the same and the only thing I need to change with setups is the interstage pressure.
• I only own Cyklon 2nd stages and a full face mask (Ocean Reef) hence why I set all the first stages up at 9.5 Bar interstage. I will separate them out and keep one at 9.5Bar for the full face mask and reset the others to 11.5 Bar for the Cyklon.
• To O2 clean the regs I used chloroform. It dissolves silicone based lubricants and then wash in water, then acetone, then air dry. I only use Christo-lube (O2 compatible silicone grease) for lubrication and vyton rings.
• Have you got any recommendations for an OPV? at least one that opens at what pressure - 20 Bar?
• Thanks for confirming the spring configuration. While I have a spare spring kit, I am leaving those as they were - they all reached 9,5 Bar and also 11,5 Bar quite happily, so no need to change what is working perfectly.

Tack så mycke for uppgifterne,

Med vänliga hälsningar

Marco

 

[mbussado]

Just for the sake of posterity, I wanted to confirm I have now dived all the second and first stages I serviced. I used to pack and ricg my own parachute, I also believe in the same for diving life support. Maintaining poseidons is 50% less effort than contemporary scubapro. All the key components are metal, o-rings, membranes or valve seat plastics. It is really straightforward and a testimony to the resilient and well though out timeless design.

I have taken the regs to 240fsw at 4 Deg C (with the antifreeze caps on) - their breathing was flawless. They breathed equally well on full tanks as they did on lower pressure (I isolated a twin set, breathing one tank down in a test matrix - I will reverse the setup in the next dive) and tested them on up to NX90 (at home).

Thank you poseidon for such a well designed system - NOTE to all, unless you are trained, you are taking a risk you should be comfortable taking!

 

[19dohc]

Dear fellow-Scubaboarder, I am a fellow Poseidon owner. I would like to have my Poseidon cyklons and jet streams looked at by a qualified service technician nearest where I live. Would you by any chance

---------- Post added November 16th, 2015 at 10:31 AM ----------

Dear fellow-Scubaboarder, I am a fellow Poseidon owner. I would like to have my Poseidon cyklons and jet streams looked at by a qualified service technician nearest where I live. Would you by any chance know of one in Vancouver ? I am at Sechelts

---------- Post added November 16th, 2015 at 10:32 AM ----------

Dear fellow-Scubaboarder, I am a fellow Poseidon owner. I would like to have my Poseidon cyklons and jet streams looked at by a qualified service technician nearest where I live. Would you by any chance know of one in Vancouver ?

 

[Caveeagle]

• The only difference between a 3950 1st stage (it's actually a 3720 1st stage) and a 3960 1st stage (it's actually a 3790 1st stage), when it comes to parts, is the o-ring you mention. The 3960 1st stage must have the o-ring if a Jetstream 2nd stage is attached to it while the 3950 1st stage doesn't need it if there's a Cyklon 2nd stage attached to it.

• The additional o-ring used on a 3960 1st stage is there to maximize the air flow through the LP ports, as the Jetstream 2nd stage design require as much air flow as possible to seal. The Cyklon 2nd stage design do not require the same high air flow rate.

Can someone confirm exactly which O-Ring is this refers to in the 3720/90 1st stage? I have looked closely and the service manual exploded view on both versions and do not see a difference (omitted o-ring).,

Also, is there any potential problem if you include that 0-ring in a 3720 (Cyklon 5000) application?

 

[tbone1004]

bringing this back up to answer @Caveeagle 's question since I came through.

It's o-ring part #2809. In the manual it is position #12 on the 3790's and position #20 on the 2960's

I don't believe there would be any problems using it with the Cyklons but since they have to be dedicated due to the IP, I usually leave it out