MK25 S600 breathing hard

[Couv]

OK....this is if you are interested and not afraid to do a little DIY and your reg has been recently checked out as correctly put together by a knowledgeable person.

Carefully take off the low pressure hose from the second stage. Be sure to use a backup wrench on the jam nut. Run the adjustment knob all the way out. Shine a light down the inlet barrel. The slotted head item you see down there is the inlet orifice. Whilst holding down the purge button (so that you do not cut the soft seat) take a thin flat blade screw driver and give that screw a 1/12th turn counter clockwise. (The way Peter Wolfinger puts it, if it were hands on a clock 5 minutes) Hook the hose up and pressurize normally. Continue these steps until you get a very slight free flow and then go back clockwise until the free flow stops.

Some people, myself included, like to tune an adjustable regulator to the point that it will slightly free flow at the max performance setting provided the free flow will stop when you bring the external adjustment knob in a bit.

It is pretty easy to check the cracking pressure of a second stage. Simply immerse the regulator in your sink with the mouth piece up. It should begin to free flow before the diaphragm is 2 inches deep. (A well tuned regulator will less than 1 inch)

Good luck, keep us posted on your results.

 

[tceylan]

Are you saying that you used to USE your primary with the knob all the way in and it breathed excellent? While I'm sure I could adjust one to perform like that, it would free flow very badly if you opened up that knob.

Yes, I kept it in lowest perf and it breathed much better than it does today with max perf setting.

(This is my first reg, so I didn't know which setting to use it really. Scubapro manual recommends a low performance setting to minimize freeflows and to turn out
the knob if the perf is not good enough. I guess I tried to follow this advice...)

 

[DA Aquamaster]

Find a new LDS. Servicing a first stage becasue it is "close to being serviced" and not servicing the second stages is pretty stupid.

If properly adjusted two S600's should have very similar (and very good) breathing performance.

 

[halocline]

Yes, I kept it in lowest perf and it breathed much better than it does today with max perf setting.

If this is true, something is wrong. Storing the reg with the adjustment knob all the way in (you should really describe it as screwed "in" or "out" for clarity) would likely cause the orifice, which is a small tubular fitting of brass or plastic (someone please tell me that the top-of-the-line SP 2nd does not use a plastic orifice!) to scribe an indentation on the seat, which is a small neoprene (or similar material) disc. In your reg, the seat has a tiny hole down the middle to provide for balancing air pressure, but that doesn;t matter so much for this problem. Anyhow, the adjustment knob tightens or loosens a spring which holds the seat against the edge of the orifice. All the way in, and you're pushing the seat much harder against the orifice, which has a semi-sharp edge. So, it gets this indentation, which means that the spring must now be tighter to hold them together. When you back off on the spring, (adjusting for "maximum" performance) and the seat has this indentation, it will tend to allow air to flow between the orifice and the seat. That's your freeflow. So, the typical result of storing the reg with the inhalation adjustment all the way in is that it freeflows when you turn the adjustment out to max. If you do this, and it does not freeflow, but instead breathes much harder, something's wrong and I don't know what.

 

[tceylan]

Thanks everybody. I will get these regs serviced and see how this goes...

 

[redacted]

(someone please tell me that the top-of-the-line SP 2nd does not use a plastic orifice!) .

think of it as soft white brass

 

[DA Aquamaster]

Sad isn't it? I have my own personal horde of brass orifices and they are interchangeable with the new "improved" white plastic ones.

Scubapro switched around 1996 as the brass orifices could potentially corrode while the plastic ones don't. I am still waiting for the brass orifice in my original 1983 SP reg to corrode. I suspect it will happen any minute now.

I also suspect the change to plastic had a lot more to do with reduced production costs. To be fair however they work better than you'd think.

 

[halocline]

Well, at least it gives those of us with old SP regs yet another opportunity to brag about how much better they are.

 

[Luis H]

Sad isn't it? I have my own personal horde of brass orifices and they are interchangeable with the new "improved" white plastic ones.

Scubapro switched around 1996 as the brass orifices could potentially corrode while the plastic ones don't. I am still waiting for the brass orifice in my original 1983 SP reg to corrode. I suspect it will happen any minute now.

I also suspect the change to plastic had a lot more to do with reduced production costs. To be fair however they work better than you'd think.

I thought that Scubapro used to say that it wasn’t plastic; it was some kind of synthetic ceramic. Or was that just BS from one of the many LDS I have dealt with in recent years?

I still have one, maybe two, original NOS brass volcano orifice still wrapped in the original wrapping paper from the early 70’s. I hope I am not going to need them anytime soon. The ones in the working regulators look just fine.

 

[redacted]

I thought that Scubapro used to say that it wasn’t plastic; it was some kind of synthetic ceramic. Or was that just BS from one of the many LDS I have dealt with in recent years?

I still have one, maybe two, original NOS brass volcano orifice still wrapped in the original wrapping paper from the early 70’s. I hope I am not going to need them anytime soon. The ones in the working regulators look just fine.

An uncautious slip of a screwdriver proved the material to be soft, like plastic. I bought a few plastic spares and modified a screwdriver so I hopefully won't need them.