Old Jetstreams

[scubafanatic]

https://www.divegearexpress.com/dgx-custom-poseidon-jetstream-single-tank-reg-package

I'm fine with keeping old gear going, within reason, but as others have indicated, Poseidons are a bit 'wierd' (just like SAABs, and the Swedish S-tank, for example), so it's debatable on how much $ you want to sink into them. Historically parts have been expensive, hard-to-obtain, and competent service techs aren't that common. Over the years Poseidon has had a very spotty record with parts availability, (related to their choice of US part distributors) and I don't know if these issues are now resolved.
Some of my first regs were Poseidon Odins, and I still own a few sets in very nice condition, although I'll admit I haven't dove them in many years. I liked how they breathed, and never had performance issues with them (other than a mis adjusted octo once.) The few annoying things I experienced were:
will free-flow at low tank pressures (at about 300 psi the 2nds will let loose and free flow) it has to do with how the 'servo valve' works.
when pressurizing the reg, keep thumb blocking mouthpiece to prevent an unexpected free flow
when pressurizing the reg, the reg will make a loud/brief 'swoosh' noise for a second which can startle you and other divers, caused by the 'balloon' in the 'servo valve' getting inflated/situated.

A while back I'd decided I'd prefer a more conventional 2nd stage with the user adjustment knob (the Odin only has an 'on-off' 2nd stage toggle switch to somewhat adjust 2nd stage sensitivity) as I prefer to have a very fine level of control over my 2nd stage cracking effort.

 

[tbone1004]

https://www.divegearexpress.com/dgx-custom-poseidon-jetstream-single-tank-reg-package

will free-flow at low tank pressures (at about 300 psi the 2nds will let loose and free flow) it has to do with how the 'servo valve' works.
when pressurizing the reg, keep thumb blocking mouthpiece to prevent an unexpected free flow
when pressurizing the reg, the reg will make a loud/brief 'swoosh' noise for a second which can startle you and other divers, caused by the 'balloon' in the 'servo valve' getting inflated/situated.

1. yes the servo valve is upstream, so needs some pressure to seal it
2. you shouldn't have to do that, have never experienced a freeflow from a venturi effect on these, but I always pressurize with the switch in the - position. that said it is very important to store them with the lever in the + position otherwise the diaphragm will deform
3. yes it is quite fun when people look and don't know what happened if they aren't familiar.

4. if you are interested in trading for any more modern reg sets, let me know

 

[tmolnes]

My jetstreams are from 97, and has 500+dives and works like new would not change it out for anything else, but thats me