Scubapro 1st stage ID?

[AquaNSun]

Hi, I need help ID this Scubapro 1st stage. It has 2 HP ports and 5 LP ports and the ambient chamber was filled with SPEC (spell right?). Are there any parts that need to be replaced if I should use it and any known issues that you know of? I got this with a R109 and interested in knowing its background. Is it ok to rebuild it and what do you think about its condition? This is my first balanced piston scubapro.

Thanks in advance.

Edit: It comes with one shim and the HP o-ring is purple color. Piston o-ring is light blue.

 

[redacted]

It is an older Mk10. Looks to be in good shape.

 

[AquaNSun]

I was checking the schematic diagram for Mk10, revison C and initially it seemed that I was missing an o-ring - item #9, 01-050-137, piston shaft o-ring. But then I looked hard and it seemed that there was a groove in the body and the o-ring was inside. It was difficult to see but I think it was there and the o-ring was light color. Anybody has o-ring sizes for mk10 and what do the colored orings mean?

 

[Zung]

Congrats for a fine purchase!

Yes, the HP o-ring is a 2-010 Duro 85, currently black EPDM with a red stripe, buried deep inside the body. If it's light in color, it's a urethane and works fine. Be very careful when you remove it, use a brass pick if you have one, and be prepared to sacrifice the o-ring instead of the reg.

There's a bunch of info's on SP o-rings here, including annotated schematics.

SP used to color-code their o-rings some 10 years ago, but now they're all black; some of the more tempermental ones are marked with a painted-on stripe, usually orange/red for the HP stem, yellow for the 2-011/85 seat, and blue for the 2-022/70 MK20 piston crown. You may want to check you color o-rings carefully. I still have some that work fine, others just crumble to pieces when squeezed,

 

[AquaNSun]

Thanks Zung.

Is the SPEC also acting like a sealant so that the ambient chamber is sealed? Looking at the ambient holes they are so small and if I don't use the SPEC it seems that rinsing the piston might be a problem. Using the old HP seat, I got a HUGE IP swing when purging. I got like 40psi dropped and then locked at 150psi. Something is not right here?

 

[Couv]

The SPEC grease is not necessary, but you must lube the piston head and stem o-rings. Your problem is probably due to reusing the old seat causing to miss-matched engraving on the soft seat.

When you put that puppy back together, put a drinking straw (or tape) over the piston end to prevent damage to the stem o-ring.

After a dive trip, you should SOAK the first stage with a good dust cap in place.


Edit: One more thing. After a rebuild, you should cycle it 20-30 times, then check the IP.

Have fun,

couv

 

[Zung]

The SPEC doesn't seal, strictly speaking; it just packs as much grease as possible inside to keep the water out and lower the freezing temperature, and make a mess of everything.

couv is right, I think your seat is due for replacement; anyway I don't like the color. Hopefully you can lay your hand on a service kit. I'd use the opportunity to replace ALL the o-rings, even those which are not in the kit; it's only a buck or so.

 

[halocline]

Thanks Zung.

Is the SPEC also acting like a sealant so that the ambient chamber is sealed? Looking at the ambient holes they are so small and if I don't use the SPEC it seems that rinsing the piston might be a problem. Using the old HP seat, I got a HUGE IP swing when purging. I got like 40psi dropped and then locked at 150psi. Something is not right here?

The SPEC grease does seal the ambient chamber, and in the case of this regulator, has also kept corrosion out of the chamber. You won't have any problem keeping it clean if you soak it after a salt water dive.

You need to use a new seat, they're everywhere on ebay. In fact, the kits come with three, so you might be able to get one at a friendly dive shop that services these, as they usually put the two they don't use in a drawer. If your IP is 150, ditch the washer and use one of the taller seats, marked with either a single I or II. Avoid the ones that have a + on the back; those are for raising the IP. There's no use even worrying about the IP drop until you get the new seat.

You also need to use a bullet (not from a gun) or some sort of dowel that will allow you to install the piston without damaging the new HP o-ring. The material and hardness of this o-ring, as well as the quality of lubrication on the piston stem, and the condition of the piston stem itself, can probably have a significant impact on the IP drop. If you want to try what I would consider to be the best option, use a new polyurethane duro 90 o-ring, lubricate it generously with either tribolube or christolube, and use some very fine abrasive like micromesh or even polishing compound to break up any glaze on the piston stem where it contacts the HP o-ring. Put a little lube on the bullet and the piston stem too.

Even so, you'll probably find that the MK10 has a surprisingly large IP drop, but 40 PSI is way out of range. 20 might be more like it, and the recovery should be VERY fast with good lock up on a new seat. Re-installing a used seat has always resulted in some creep for me.

Have fun!

 

[Zung]

For removal and installation of the HP stem o-ring, chech these posts out, #28 & #27.

For me, it's the hardest part in servicing the MK5/7/10.

Regarding IP drop, I just went through my notes, and most of mines drop in the 1-2 bar/20-30 PSI range, with a G250 second.