Scubapro S600 free flow

[mick allein III]

All: I went piece by piece and discovered the problem was the seat. The mk 25 will remain stable at 144 for hours. Here how it breathes. When initially charged it will have a IP of 138. When I breathe it it cycles back and forth between 138 and 130 or so. When I stop breathing it and turn down the micro adjust on the s600 to prevent leaking it will creep to 144 IP and remain there for at least 2 hours. Is this typical in your experience.?

I've tuned the s600 and am ready to pool test followed by some shallow dives <20ft.


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[Couv]

All: I went piece by piece and discovered the problem was the seat. The mk 25 will remain stable at 144 for hours. Here how it breathes. When initially charged it will have a IP of 138. When I breathe it it cycles back and forth between 138 and 130 or so. When I stop breathing it and turn down the micro adjust on the s600 to prevent leaking it will creep to 144 IP and remain there for at least 2 hours. Is this typical in your experience.?

I've tuned the s600 and am ready to pool test followed by some shallow dives <20ft.


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Off the top of my head, I would say that is too much creep. Also, 144psi is right at the upper edge of SP's IP specs; however, I think Zung, Halocline, or Awap could better address the MK25 issue as they have dealt with the idiosyncrasies of that first stage, composite pistons, and more importantly Matt Magic.

Getting back to the second stage. After you obtained a steady IP, you tuned it and it solved the freeflow? Is that correct?

 

[mick allein III]

Zung, Halocline, Awap chime in. I'm interested. As for the free flow, I have not yet dive it but I am pretty sure I have it tuned. It seems very stable when I breathe it different ways. Submerge it etc.


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[redacted]

I would troubleshoot the 2nd stage on a 1st stage that I know is good. A new HP seat with a good clean piston should lock up solid. Over time you will start to see some creep and I don't usually try to fix that until it get to be about 10 psi.

In this case, it may well be that the IP creep you are seeing is not actually locking up but is just being relieved by the leaking 2nd stage. One thing you might try is to lower the IP setting on the 1st stage to 125 to 130 and see what it does.

In any case, I suggest you do everything you can to determine where the leak is occurring in the S600 before you start swapping parts. I would not expect the problem is the LP seat or the orifice knife edge as they should respond to adjustment knob changes. And the two small o-rings on the end of the poppet priovide a redundancy unless both are bad (unlikely). So I would still be looking at the other balance chamber o-rings and the orifice o-ring. A defect in any of them could produce the symptom of being uneffected by the user adjustment knob and of being depth sensitive. In fact, the depth sensitivity make me wonder if an o-ring might have a bubble inside the material.

Good Luck

 

[mick allein III]

Very helpful. Thanks


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[Zung]

Happy new year!
Sorry I'm late, just back from the Maldives, and yes, it was good, we saw sharks on a daily basis, small, medium, even a zebra shark, not common over there

I second the Master 100%, so my short version is: leave the 1st stages alone, and debug the seconds.
Now, to add more meat to this:

The Mk20-25's can act funny sometimes (make it often): right after service, the IP locks up solid and stay put, but it can drift a bit between dive vacations, which, in my case, is yearly. Not a lot, 5-10 PSI or half a bar or so is common with my "active" set of 5 (4 + 1 spare); nothing to worry about, certainly not enough to cause any free flow with balanced second's such as the G250/156.

After some activities, the drift goes away, so I suspect it's some grime that somehow got in from the previous expedition, or the piston that rotates a bit; again, nothing to worry about, ignore it and it goes away.

While preparing the last vacations, I came across 1 case of free flow from a G250; it went away after a good cleaning, so it was again some grime that got between the orifice and the seat.

I'll set up a test this weekend and report back with some hard numbers.

Cheers.

 

[Zung]

Test done, but nothing new: I've got only 1 MK25, the wife's, last dive was 1/1/2015 where a zebra shark and a small black tip were sighted; its history is reported here and here.

The tank has 90 bar/1300 PSI. The IP swings to 8.75 bar/127 PSI immediately, then takes about 5 minutes to creep to 9 bar/130 PSI where it stays for a couple of hours before I end the test.

Again, nothing to worry about.

The only lesson learnt: while purging, the second stage spits out a sizable amount of water, also the BCD inflator hose; it has been soaked overnight and left to air dry. The water would have stayed inside, possibly leaving some residues that could cause some (temporary) issues if tested dry. Now I'm purging every other regs.

 

[mick allein III]

Zung. Thank you. That's about how my MK25 behaves..


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[ams511]

How old is the MK-25/S-600? and how many dives? I am wondering if the non-replaceable parts are starting to show wear. I mean no offense but how experienced are you at regulator servicing? Could it be possible you damaged an o-ring during replacement? Again no offense intended, it happens to the best of us at one time or another.

 

[mick allein III]

No offense taken. Maybe 100 dives on it. I'm not experienced with working on regs. Just starting. I am going to rebuild both shortly. Just start over


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