scubapro d400/mk10 questions

[halocline]

i believe my reg is the pre 1995 fom the design on the purge cover, does that mean it does not have the plastic orfice? i am new to diving and would this be fine for a long lasting reg? how well do they work in cold water? is there anymore of a chance of free flowing than any other regulator?

If you're planning on diving the set in very cold water (not in FL!) you might want to consider having the ambient chamber of the MK10 packed with environmental grease, like PTFE (or silicone grease if you're diving on air). If your MK10 has a groove in the ambient chamber, you might be lucky enough to find the SPEC boot that fits it. Then the grease really stays put; but if not, you can still pack it, just a little will seep out over time.

It's likely the reg will outlast you if you take good care of it. There should be rebuild kits available for another few decades.

 

[gigihurt]

thanks for all the info. i just wante a basic understanding of what i have and what to look for. when i get the money i am having everything serviced then i will post how well i think the d400 is. which i am thinking that there will be nothing to worry about with it.

 

[DA Aquamaster]

If you are not sure about the techs in your area, I'd be happy to service it for you.

I don't have much in terms of two gauge consoles, but I can check. However if you want another D400 second stage or an R156 Balanced Adjustable to replace your current unspecified octo I have a few available.

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Packing the ambient chamber has pros and cons. In fresh water it works well. In salt water however the salt water tends to get trapped in voids in the silicone and cause corrosion.


More importantly, unlike the earlier Mk 5 and later Mk 15, 20 and 25, the Mk 10 has the bearing surfaces for the piston head o-ring in the body of the first stage rather than in a separate (and much cheaper to replace) swivel cap. This has two significant impacts. First the piston sits down inside the reg body and makes it much more difficult to fully pack the ambient chamber in the spaces near the bottom of the chamber and around the spring. In most cases, silicone just got squirted through the ambient pressure holes after assembly with the Mk 10, and that method of packing results in significant voids that over time fill with and retain water. Second, when the first stage is unpressurized, the piston stays at the top of the stroke, exposing the bearing surface to what ever water may be trapped in the silicone. During storage then, this water potentially has time to work on that surface and corrosion is more likley. If/when corrosion occurs in this area, the whole reg body must be replaced and Scubapro does not make those any more.

In contrast with the Mk 5, Mk 15 and early Mk 20, which also used a silicone filled environmental chamber, if this bearing surface were corroded, it only cost about $20 to replace the swivel cap. And since the piston sat on top of the reg body, it was easier to fully pack and could be done with far fewer voids.

The Mk 10 was the only SP piston reg to use that particular approach to the ambient chamber. it was done as the Mk 5 was prone to production isuses with less than perfect alignment of the hole for the piston stem in the reg body and the bearing surfaces in the swivel cap as it required very precise maching of the hole, the swivel cap and the threads and bearing surfaces between them. The design of the Mk 10 allowed the hole and the bearing surfaces for the piston head o-ring to be done in one pass with perfect alignment and the precision of the threads and turret retainer were no longer critical.

However, due to the other problems the design caused - the above mentioned corrosion issue as well as the need for a smaller diameter piston head which has significant downsides - Scuba pro went back to the older Mk 5 layout in the Mk 15, 20 and 25 as newer CNC technology allowed the required precision at acceptable production costs.

Unless you are diving in really cold water I'd recommend leaving a Mk 10 alone and not filling the ambient chamber.

 

[halocline]

Second, when the first stage is unpressurized, the piston stays at the top of the stroke, exposing the bearing surface to what ever water may be trapped in the silicone.

Are you saying that the reason the water would be present near the piston is because it's more difficult to get the silicone up in that part of the ambient chamber or because the piston will move away from the grease, creating a void, when depressurized? What about packing the piston/spring before installing it? That's what I did, then also added a little down around the HP o-ring end of the chamber, then assembled and watched the excess grease come out the ambient chamber holes. I was pretty careful to make sure the chamber was packed, not just filled.

I got curious about it because I bought a MK5 that had been packed and the ambient chamber and piston head looked PERFECT, even though it had not been serviced in several years. Now I have 1 MK5 and 2 MK10s packed, I'll be interested to see how they look when I rebuild them.

Of course, there is no 'reason' to do this except for very cold water use, as I think I also mentioned in response the OP's inquiry about cold water use.

 

[DA Aquamaster]

Yes, that's it exactly. With the piston inserted in the body of the Mk 10, there is not much room to work with so you do some of the packing in the body and around the spring before inserting the piston, while trying to avoid getting goo past the piston stem o-ring, then you pack some more then you fill then you pressurize and wipe off the excess.

With the Mk 5 where everything is pretty well exposed aftter the piston is in the reg body, you can pack around the step in the bottom of the ambient chamber, pack the spring, piston stem are and the piston head inteface and then install the swivel cap, fill , pressurize and wipe off the excess.

It's easier to get a better result with a Mk 5 than it is with a Mk 10. When poorly done, you end up with a lumpy inconsistent mass of dirty, watery silicone in the ambient chamber with water in contact with critical parts of the regulator body.

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Cold water is hard to define. My technical diving started in areas where "warm" water was 55-65 degrees and "cold" water maybe 35-45 degrees. After a 30 minute bottom time in 35 degree water, deco in 60 degree water feels bath tub warm.

If "cold" water is 55-65 degrees, I woudl not mess with it. If we are talking cold water as being in the 35-55 degree range, then it is worth the trouble.

Before I switched to the Mk 17 I used early Mk 20's with the later Mk 15/early Mk 20 SPEC boot and silicone filled environmental chambers for very cold water technical diving.

 

[drbill]

I use Mk10 first stages almost exclusively (I do have one Mk2+ for a pony bottle), but they are paired with G250 second stages. Absolutely love that combo. Effortless. Years ago I used the Classic BCD, but switched to a SP X-Tek soft harness about 10 years ago and it is the only BCD I use today (currently paired with a HOG 32# donut wing thanks to Dave and Sue with Indian Valley SCUBA).

 

[Zung]

Has anybody done any accounting? An oz ($15) of Christo/Tribo-lube to pack?
The official repair guide says 7gr/.25oz, but that seems a bit optimistic.

 

[Shftrdog]

I think you should get the Oceanic VEO 1.0 computer to go with it instead of gauges. It is not that much more and you get a computer with it.

 

[DA Aquamaster]

Has anybody done any accounting? An oz ($15) of Christo/Tribo-lube to pack?
The official repair guide says 7gr/.25oz, but that seems a bit optimistic.

I don't think Christo Lube or Tribo-lube are viable options unless you are using a later Mk 10 with the rubber boot.

Scubapro used a particularly thick grade of silicone in their SPEC kits - much thicker and stickier than for example the silicone you get from trident, and not even in the same ball park as Christo Lube or Tibo-lube. Consequently, while the older Mk 10 with the small SPEC holes but no boot could do ok with the Scubapro silicone, they leak a lot more with the trident silicone. The later model Mk 10 with larger ambient pressure holes and the SPEC boot, will be tough to keep filled without the boot due to the larger holes. Add Christolube or Tribo-lube to the equation and you just get a much more expensive and runny maintenece problem.

And realistically if it's a back gas reg, there is no real reason to use an O2 compatible lube in the ambient chamber. I'd still use christolube or tribolube on the dynamic o-rings, etc, but there's no need to use it in the ambient chamber, especially given the amount required.

 

[Zung]

Thanks for the clarification.

I once bought a 1/2 oz synringe of Christo; 2 years and over a dozen regs later, it's still about half full. I was wondering who's brave enough to pour the whole tube down 1 single reg.