Local Pawn Shop find: double Xstreams

[tmassey]

The second stage has lovers and haters, but as a side exhaust, it just shouldn't put bubbles in your face. I don't get that complaint, Tim.

What can I say. I’ve used XStream seconds and Jetstream seconds. Multiple dives each time I’ve tried, and I’ve tried multiple times with each design. I dive them with a long hose, without a 90* elbow. When I do so in horizontal trim, I get bubbles across my line of sight and they get caught in my hood. Even 20* head-up trim tends to lessen or eliminate that. But in solid horizontal trim i get bubbles and a cold head.

I’ve been told this is less of a problem when the hose isn’t “hog tied” around your neck, or by putting a 90* elbow (or swivel?) on it. I’m really not interested in either of those work-arounds, so I just keep diving my Apeks clones.

And maybe the fault is my big, bulbous head. While you may not “get” my complaint, I certainly do. But it’s just an anecdote, and my N only equals 1…

I mentioned the “throwing air” issue but I’ve never really considered it that much of an issue for me. I just know others do. I will say: be careful hitting that purge button! I’ve frozen a second stage on a cold (but not ice) dive, and I’ve caused myself to choke from high-speed droplets hitting the back of my throat: put your tongue in the mouthpiece first!

Like I said, I really want to like them. They are the coolest piece of regulator engineering I’ve ever seen. But even if your IP settings make them breathe exactly like any other reg, I don’t think it’ll solve my exhaust issue…

But heck: I still have a set of XStream firsts with Jetstream seconds (plus some Odin firsts with OPV’s)…. What’s another try gonna cost me?

 

[happy-diver]

However, $340 is a steal, and if they’re asking $340, I would offer $300: I’m certain that’s what they expect to get when they have a price of $340!

Didn't the guy from Pawnstars suggest you offer him $260 so he can meet you half way at $300 dude

 

[wdeutsch]

Just a thought from another angle...

Around here, most of the good stuff at pawn shops is stolen goods. Sure, there are laws that the shops can't sell stolen merch, but when you read the details, all that means is they can't sell items without first "asking" the local police dept if it's listed in their records as being stolen. If the police don't respond within a set time (usually a couple of weeks) then the shop is cleared to sell it, and most of the police agencies here don't have the time/staffing to keep up with the pawn shop records requests. So, effectively, they can sell stolen goods with no liability. Also, the folks stealing the goods know to pawn it out of their local jurisdictions to make it less likely it's discovered.

It's up to you whether you want the Juju associated with diving (likely) stolen kit. But, ask yourself how likely it is that someone legitimately pawned those for $200 or less, instead of selling themselves.

 

[randini]

I went back this morning. While I was talking with the shop manager, he showed me the shop's history and they bought them in 2019 for $450.

There's not a lick of corrosion or salt on them. I wonder if they've ever been diving (other than that pinch of sand that was in the reg bag). IP locked up at 9.0 bar with a 3000psi tank. And I see what you mean about air being shot out of them.

For now, I'm the happy owner of a set of Poseidon double tank regs. Thanks for the advice and guidance.

 

[happy-diver]

It's up to you whether you want the Juju associated with diving (likely) stolen kit.

Yeah hey like my accumulation of milk crates but it's ok I put myself on home detention with day release

 

[mictrik]

After spending tons of new hours with these regs, it is clear that Poseidon has done its divers and its brand a disservice with its tuning recommendations and diver education.

Quite simply, the Xstream first stage is the best diaphragm reg in the world. Hands down. Having now rebuilt dozens of old regs from the previous training program, there was not a single reg that I couldn't get to lock up crisply with a new service kit, no matter how beaten up.
The gas flow path is smoother than any other design, and there is only one (semi-dynamic) high pressure o-ring, compared to three in a Mk17/19. That means less particulate damage to the components, and a longer lasting lockup. The ruby ball is self-centering.

The second stage has lovers and haters, but as a side exhaust, it just shouldn't put bubbles in your face. I don't get that complaint, Tim.

But this complaint about "blowing at you" is a recurring one. I'm in discussions right now with Sweden about their official stance. But from a personal standpoint, that should be about 80% reduced by using an IP at the low end of specification (109-115 psi), and a dynamic inhalation resistance of 1.1" during a very light breath. There are just a whole host of tuning errors made by the shops. And it's hard to bring yourself as a DIY'er to set your IP at 110. But that's what I do for my personal regs. It meets EN250 at 109, so I'm not even worried with deep dives at that IP. Seventy-two holes in the second stage outflow track makes for great gas delivery.
It's "different" in shallow water, but just a little if tuned light with a low cracking effort. And that disappears at 40 feet.
The other 20% of "blowing at you" is inherent in the design, and frankly is a better way to breathe at high gas density. The valve is on/off, not "barely to wide open" depending upon suck. And that's really only perceptible in the first 40 feet. Below that, increasing ambient pressure really mutes it. But it's better, because it prevents our surface habit of sipping a tiny breath. At depth, that's just exchanging dead space and is not the right way to breathe off scuba gear. It won't decrease your gas consumption.

If I spent most of my time 40ft or less, I might even choose another second stage myself (still attached to an XStream first). I'd have no need of the benefits. But there are not very many regs that meet Norsok standards and are  certified to 600'.

The Deep and Deco difference is just oxygen cleaning and a different service kit and trim color. But the HP seat (Zytel 103) is the same for both.

I like the "mechanical breathe" and blast of air that comes with it. You are never wanting and always feel assured. I prefer the original G250 high venturi to more modern versions for a similar reason. To each his own.

 

[growcurlyhair]

After spending tons of new hours with these regs, it is clear that Poseidon has done its divers and its brand a disservice with its tuning recommendations and diver education.

Quite simply, the Xstream first stage is the best diaphragm reg in the world. Hands down. Having now rebuilt dozens of old regs from the previous training program, there was not a single reg that I couldn't get to lock up crisply with a new service kit, no matter how beaten up.
The gas flow path is smoother than any other design, and there is only one (semi-dynamic) high pressure o-ring, compared to three in a Mk17/19. That means less particulate damage to the components, and a longer lasting lockup. The ruby ball is self-centering.

The second stage has lovers and haters, but as a side exhaust, it just shouldn't put bubbles in your face. I don't get that complaint, Tim.

But this complaint about "blowing at you" is a recurring one. I'm in discussions right now with Sweden about their official stance. But from a personal standpoint, that should be about 80% reduced by using an IP at the low end of specification (109-115 psi), and a dynamic inhalation resistance of 1.1" during a very light breath. There are just a whole host of tuning errors made by the shops. And it's hard to bring yourself as a DIY'er to set your IP at 110. But that's what I do for my personal regs. It meets EN250 at 109, so I'm not even worried with deep dives at that IP. Seventy-two holes in the second stage outflow track makes for great gas delivery.
It's "different" in shallow water, but just a little if tuned light with a low cracking effort. And that disappears at 40 feet.
The other 20% of "blowing at you" is inherent in the design, and frankly is a better way to breathe at high gas density. The valve is on/off, not "barely to wide open" depending upon suck. And that's really only perceptible in the first 40 feet. Below that, increasing ambient pressure really mutes it. But it's better, because it prevents our surface habit of sipping a tiny breath. At depth, that's just exchanging dead space and is not the right way to breathe off scuba gear. It won't decrease your gas consumption.

If I spent most of my time 40ft or less, I might even choose another second stage myself (still attached to an XStream first). I'd have no need of the benefits. But there are not very many regs that meet Norsok standards and are  certified to 600'.

The Deep and Deco difference is just oxygen cleaning and a different service kit and trim color. But the HP seat (Zytel 103) is the same for both.

sorry to revive this thread, but would like to have a penny for your thoughts on these regs.

I have 2 sets of poseidon xstream regs that i bought used (from someone migrating to another country), last serviced Oct-24.

I tested them both before hitting a pool with them. One set was freeflowing very hard, and the other had the signature sudden blowing before i had to blow into the mouthpiece, after which it calmed down.

I took the "ok/calmed down" set out for a shore dive, but found inhalation requiring a bit more WoB than usual, which made me quite uncomfortable and i swapped out for another set of regs after.

The service here locally is about 250 usd a set for poseidons.

I'm trying really hard to weigh the pros and cons of using this as a primary set of regs (after a service) or getting a scubapro set instead. To be honest i would like a reliable workhorse, in which the reg isn't at 0% or at 100%, which is what my understanding of these regs are. Unlike the more "standard" regs where they operate fully most of the time. The dive shop commented that these need to be babied. Then again they are not official poseidon service centres, but are experienced in servicing it.

Appreciate the advice on the latter. Thanks in advance.

 

[rsingler]

This applies to any brand: if you don't have trustworthy service, buy the set that local techs know how to rebuild. Poseidon may not be that brand for you.

But no. They don't have to be babied. The US Navy uses them, including the SEALS. They can take a lot of abuse. The first stages last forever, and the seconds just need care with the servo valve.

Your issues with freeflow are likely just a simple tuning problem, tho' you might need a new servo and/or diaphragm. Your abrupt breathing is as described above: your IP is too high. Tune it to 118 psi/ 8.1 bar at full tank and it'll perform much more smoothly.

 

[growcurlyhair]

This applies to any brand: if you don't have trustworthy service, but the set that local techs know how to rebuild. Poseidon may not be that brand for you.

But no. They don't have to be babied. The US Navy uses them, including the SEALS. They can take a lot of abuse. The first stages last forever, and the second just need care with the servo valve.

You're issues with freeflow are likely just a simple tuning problem, tho' you might need a new servo and/or diaphragm. Your abrupt breathing is a described above: your IP is too high. Tune it to 118 psi/ 8.1 bar at full tank and it'll perform much more smoothly.

Thanks! Will take this advice and bring it to the local techs.

Just so i can understand a couple of things:

1. Does the servo-style breathing make it more uncomfortable to breathe from? I get that its supposed to be different, but i guess its hard to really know until i try it post-good service

2. "and the second just need care with the servo valve" <- how do i take good care of this?

Thanks!

 

[rsingler]

Having a servo does not imply harder breathing.
As with all things scuba, it comes down to tuning. An Xstream tuned to 1.1" at an IP of 109-123 is sweet. It's the onset of the breath that is slightly more "square wave" than with a lever design. A lever valve goes from "barely cracked" to full flow based on how hard you suck, with at some point Venturi kicking in and maintaining flow at less effort until you exhale and shut the valve off.
In contrast, a servo design is like a trigger. The transition from servo valve opening to main valve opening is very short, and having a high IP makes the sensation almost uncomfortable, simply because the Poseidon outflow is so large. It works, but you don't need that much gas.
The other problem is vocabulary. The Poseidon service manual says "cracking effort". But it's not! It's dynamic inhalation resistance. It's supposed to be 1.1" during a very light inhalation. If you tune it so the servo doesn't crack until 1.1", main valve opening won't be until 1.4"+.
Make sure your tech tunes it so the effort is 1.1" during a tiny breath, and not when the servo cracks open.

A great resource in the service manual is the field tuning technique described on page 40 of the manual. A simple dip into a water basin can measure your cracking effort just as precisely as with the magnehelic! But again, the problem is vocabulary. What the manual calls "sizzling" is not the tiny champagne bubbles of servo opening, but the slight flow as the main valve begins to open. It requires practice to develop a technique of slowly immersing the second stage (purge button down and vertical) until the main valve starts to open. When that starts to happen, you need to quickly pull back 1/4"-3/8", before water is sprayed everywhere. When you find that stable light flow depth, the distance from there to the center of the purge button is your dynamic inhalation effort in inches WC. For optimal light tuning, that stable flow depth should be at the top of the lower necklace loop. Easy, peasy, albeit requiring a little practice. And if you need to retune the reg? A 1.5mm hex key to loosen the hex stop and a surgical forceps will rotate the valve tube closer to, or farther away from the diaphragm, to lower or raise breathing effort, respectively.

Don't use your finger tip to depress the purge button. Use the flat of your finger - it's a trigger. You don't get more flow from pushing harder, and if you jam your fingertip into the button, you can tilt the servo past its 35° limit and bend the shaft. That's unrepairable and requires a new $65 part. They tried to engineer that out with a very stiff purge button, but that just means a SEAL will jam harder. It's a real issue for the Navy because it requires a change of habit, and that comes slowly.

SOAK your second stages overnight in the sink after a dive trip. It's hard to get the salt out of the crevices with just a flush. Salt crystals accumulating in the tiny servo valve may cause it to stay open. If you are adept, and have a scuba tank, with regs unpressurized, consider pressing the purge button for a ONLY a half second with the diaphragm end of the seconds hanging vertically in the sink, with the purge button end just below the water's surface. Don't submerge the entire second stage. This will allow a tiny bit of fresh water to flow around the servo valve. Let it hang vertical on a towel bar for 20 min, then pressurize the reg set and barely push the purge button until you can hear gas escaping from the servo, but before the main valve opens. Let it hiss a bit to dry out the servo and you're done!
Unfortunately, that's too complicated to put in the service manual, because if you flood the whole top end, the valve will not function and will freeflow until the reg is disassembled and the main valve is dried. That's because the valve shuts off from gas passing through a calibrated tiny hole into the servo compartment. If you plug that hole with water, the main valve won't close.
It's an extraordinarily elegant and yet simple mechanism, but some Swedish overengineering has created a few pitfalls for those unfamiliar with the valve.

credit goes to my friend @Fibonacci 's superb drawings.