Scubapro S600 buying advice

[halocline]

T
I do not know why ScubaPro Will not develop a sealed piston Reg.
if they did i would go back to a Piston Reg.

If you're looking for a project, get a MK10 or MK5, find a SPEC boot (I don't know if they made them for the MK5) and fill the ambient chamber with Christolube.

 

[Age]

The MK11 is a Diaphram reg,the Diaphram reg seals the working parts.
But the Piston reg some of the Moving parts are exposed to water.
Plus the MK25 flow rate is alot higher then the MK11.
The MK25 will breath better at depths,but will tend to freeze in real cold water.
I do not know why ScubaPro Will not develop a sealed piston Reg.
if they did i would go back to a Piston Reg.

Thanks to this post I now understand why the DIR crowd are happier to flood a piston regulator than a diaphram reg: many of the parts are exposed to water anyway. I didn't know that.
BTW I have no idea what MattBoy is talking about

 

[halocline]

You might get ahold of Vance Harlow's book on reg repair (airspeed press) or just take a long look at some 1st stage schematics to get an idea of the difference between piston and diaphragm design. Both designs have an ambient chamber where water goes to allow the reg's IP to increase with depth. The only difference is that on a piston reg, there is an o-ring that seals off the dry chambers, and since a piston shaft goes through it, there is a tiny length of piston shaft that is alternately in the ambient chamber, exposed, and in the HP chamber, dry. This is not really a contamination problem, but can cause freezing in extremely cold water.

Traditionally piston regs have been "sealed" for cold water by filling this ambient chamber with grease that keeps the water off the piston shaft.

The bit about deliberately flooding the 1st stage, like if you had to switch 1st stages under water, is something different. The theory here is that the piston is more durable and can withstand the incompressible water passing through the HP area, into the IP chamber, and out to the 2nd stage.

 

[Age]

You might get ahold of Vance Harlow's book on reg repair (airspeed press) or just take a long look at some 1st stage schematics to get an idea of the difference between piston and diaphragm design. Both designs have an ambient chamber where water goes to allow the reg's IP to increase with depth. The only difference is that on a piston reg, there is an o-ring that seals off the dry chambers, and since a piston shaft goes through it, there is a tiny length of piston shaft that is alternately in the ambient chamber, exposed, and in the HP chamber, dry. This is not really a contamination problem, but can cause freezing in extremely cold water.

Traditionally piston regs have been "sealed" for cold water by filling this ambient chamber with grease that keeps the water off the piston shaft.

The bit about deliberately flooding the 1st stage, like if you had to switch 1st stages under water, is something different. The theory here is that the piston is more durable and can withstand the incompressible water passing through the HP area, into the IP chamber, and out to the 2nd stage.

Thank you for explaining. I can't say that I'm planning to put Christolube in my MK25, but it's good to understand a little more about the tools that keep us alive underwater.
Speaking of which, I tried out my new rig yesterday at the pool practicing airshares, stress training etc.etc. and I was amazed at the difference between my primary G250V and the S295 bungeed around my neck. It's true that I had them tuned as you suggested, but that doesn't fully explain the ease of breathing experienced with the new second stage. I didn't think there would be any significant performance improvement until I was at 30 metres or so, not three, so I'm a very happy diver/consumer. Only problem I can see now is that the MK11 is now redundant as the "Scubapro certified combinations" does not recommend MK25/S295. Not sure why.

 

[DA Aquamaster]

Only problem I can see now is that the MK11 is now redundant as the "Scubapro certified combinations" does not recommend MK25/S295. Not sure why.

I can't speak directly for how SP does things in Japan, but in the US the regulator combinations that are offerred are based on marketing. The idea is to create beginner, intermediate and advanced level regs, I suppose in hopes of selling three regs to a diver in their career, or alternatively in hopes of selling them a Mk 25 S600 up front arguning that it will be cheaper in the long run than buying a less expensive reg that meets their current need.

So essentially you can get a Mk 2 with an unbalanced seocnd stage for an entry level reg, or at the intermediate level you can get a MK 11 or Mk 17 with either a balanced or unbalanced second stage, or you can buy a Mk 25 with a balanced second stage.

They have reinforced this lately by removing the adjustable flow vane from their unbalanced second stages, so if you want that feature you have to pay for a higher priced balanced second stage and that also means paying more for a balanced first stage as well. It ends up being a lot more money for a $5.00 part.

The good news, that almost always goes unspoken, is that you can order any SP second stage with any SP first stage and they all work fine with each other. You lose a few percent in terms of the package discount, but that is more than offset by the savings from not having to upgraded to a more expensive first or second stage you don't want.

 

[Age]

So, to be absolutely clear, my MK11 is, in fact, absolutely fine with my new G250V?

 

[DA Aquamaster]

Absolutely.

 

[squidster]

So, to be absolutely clear, my MK11 is, in fact, absolutely fine with my new G250V?

Your MK11 is an Overbalanced diaphram fist Stage that should be matched up with a Balanced second stage ,so theG250v would work as well as on a MK17,orMK25.
Very good Second stage choice.

 

[ocpaul]

The good news, that almost always goes unspoken, is that you can order any SP second stage with any SP first stage and they all work fine with each other. You lose a few percent in terms of the package discount, but that is more than offset by the savings from not having to upgraded to a more expensive first or second stage you don't want.

OK DA - it seems like you know your stuff, so I am seeking some advice. One of my two 15 year old MK-10s has been pronounced not worth fixing by LDS. It has seen a decent amount of use and probably hasn't been maintained as good as it should have been. I'm sure it could be fixed, but it started to sound like the cost of doing so was going to rival that of a new 1st stage.

My normal setup uses a couple of G250s (1994 vintage), one on a 7' hose and the other bungeed around my neck. I have been OK with performance of G250s and have only occasionally had issues with flow from the backup when entering the water. Proper tuning seems to have taken care of those issues.

SO - the question is what 1st stage would you switch to? The MK17 seems to be favored by many, and even though cold water diving is probably not in my future, the sealed chamber kinda sounds like a good idea to me.

OR - would you use this opportunity to migrate to a complete new setup?

As far as I know my 2nd MK-10 is OK. It hasn't seen much use, but has been maintained.

Thanks in advance for your insights.

OC

 

[halocline]

Sure, buy a whole new set up and I'll be happy to take those G250s off your hands. I wonder what's really wrong with the MK10? What did they say at the LDS? Wait, don't tell me...something about your life being worth a new titanium MK25.