Scubapro balanced adjustable second stage freeflowing

[MarkH]

I got a free set of regs recently. One of the second stages is a Scubapro balanced adjustable. I wanted to try replacing my Conshelf 14 second stage with the balanced adjustable so I overhauled it (including with a new poppet). My problem is that I can't get it to stop freeflowing except when I turn the adjustment knob all the way in. Even then, air hisses by intermittently after I purge it. I'm doing this with the diaphragm and cover off so the lever height doesn't come into play. It's acting like my intermediate pressure is too high, but it's around 139 psi (with my Conshelf 14 1st stage) and these Scubapro second stages are supposed to be good for 125-145 psi. I also have a Scubapro MK5 and 109 on my bailout bottle. I've rebuilt and adjusted that reg a couple of times before with no issues.
Any ideas?

 

[rjack321]

LP seat is probably old, trashed, or cracked.

 

[MarkH]

LP seat is probably old, trashed, or cracked.

The new poppet came with a new seat installed in it. It looks fine and smooth. The poppet is the upgraded "S" poppet. The old one from the 1980's didn't have a replaceable seat, you had to replace the whole poppet. Maybe I'll try re-installing the old poppet (even though it has a groove worn in the seat) and see if I still have the freeflowing issues. I've re-built several different regs over the years (mostly my Conshelf XIVs, but also Scubapro MK5/190, Oceanic, Sherwood, Poseidon Cyclon 300, etc) and I've never had any issues. I followed the service manuals for adjustment and they always turned out fine.

 

[lexvil]

You may need a different lever, do you have a picture of the parts? Can you remove them to show the orientation and which spring/balance chamber you have.

 

[MarkH]

You may need a different lever, do you have a picture of the parts? Can you remove them to show the orientation and which spring/balance chamber you have.

I'll take some pictures tomorrow. I assume the spring and balance chamber are the originals. The spring is much thinner/weaker than the one in the unbalanced 109's. The lever seems identical to the one on my 109 second stage.

 

[johndiver999]

What about the orifice? Is it perfect?

 

[MarkH]

What about the orifice? Is it perfect?

The "volcano" orifice seems fine. I haven't looked at it under a microscope or anything, but it seems the same as the one from my 109 and that one works fine. I found a reference online to a different "curly" lever. I wonder if upgrading from the old poppet to the S poppet requires this lever change as well.

 

[axxel57]

A bit odd…

But these regs are decades old and have been used sometimes extensively, so checking the single valve components is important.

The S-Wing Poppet should be good since new, so the small o-rings should be good, but checking them in the balance chamber is always a good idea.

The orifice seems to be okay, the LP Seat new, so my concentration would be on the spring and the imprinting orientation and marks on the LP Seat.

You have tried already a couple of times valve mechanism, so there should be to see some marks on the seat.

Check if they are even in depth and orientation.

If one side has deeper marks than the other, then the spring might exert for whatever reason an uneven pressure on the seat.

The spring could be slightly bend, one little piece on the base might have broken off, or the ‘base’ on the balance chamber or even on the S-Wing Poppet is imperfect.

Usually get the springs with time ‘harder’, because slightly shorter, but I have found also very soft springs (no idea why).

If you can compare your BA spring with another BA- R-Series- G-Series (not G250V) – most of the S-Series - 080 spring (they all use the same 01.020.216 spring), you might feel a difference and could swap it for a try.

I once had even a 2nd with the orifice threads so damaged, that the orifice finally sat uneven on the LP Seat, making the cracking effort quite hard.

Concerning the lever, so normally you don’t have to change the lever to get good results, but of course you have to remove and inspect the lever to see if it is bend or the feet are not straight and parallel.

If your BA is an upgraded 109, then also the old ‘rubber’ membrane can cause sometimes some free flow, because it is very ‘flat’ and doesn’t have the flexibility and ‘response’ as the silicone ones.

Apart from free flow or not is it often a good idea to polish the center plate of the membrane to get the best results concerning smoothness and ‘response’ of the valve mechanism.

Anyway, after what you described, my guess would be that there is a problem with the spring, just check it.

Good luck!

 

[scrane]

Personally, I would start out by setting the Conshelf to 130-135 and screw the second stage orifice in a touch. If that doesn't work I'd go shopping for a new orifice or spring. You might need a new lever, but as long as you have some flop in your lever with the diaphragm removed that isn't your immediate problem. Is the passage from the seat to the balance chamber clear? Proper seat? Smooth movement and rebound with the balance chamber with the seat hole blocked?