mk10 1st stage upgrade?

[omeko]

Hi all,

I recentely purchased a second hand Scubapro mk10 regulator. It was looking exeptionally well and after taking it apart and fitting it together again I noticed that the Intermediate Pressure was going up and down a bit. My doubts were confirmed when submersing the first stage: bubbles from the centre hole at the bottom.

Now this one is really Stone Age and it hadn't had the recommended upgrade to 10+.

From the drawings I guess SP tackled this common problem by inserting an o-ring into the valveseat [is that english?].
Does anyone know if they have made any other adjustments to the seat or the piston? I guess getting an o-ring into the seat should eliminate the problem of leaking air to the outside, but is not what I would call a solution for a leaking piston seat...

Any insights much appreciated!

Marko

 

[scubapro50]

Been diving with a MK10 for over 10 years that I purchased used ..... local dive shop upgraded it a few years ago and I really couldn't tell the difference but I was told the 1st stage would run better and have less problems ..... I own 7 regulators and this is my favorite one to dive with.

 

[drbill]

I dive with nothing but Mk10/G250's and love them. Not sure about the changes though in the 10+ (sorry).

Dr. Bill

 

[DA Aquamaster]

The Mk 10 Plus uses a different piston with a rounded seating surface similar to what was used (with only limited success) for a while in the Mk 20. The seat in the Mk 10 Plus is also concave and is very similar to the seat used in the Mk 15, 20 and 25.

This seat design uses an o-ring midway down the lenght of the seat that seals between the seat and HP cap and uses another o-ring on the HP cap itself to seal between the HP cap and reg body.

The Mk 10 on the other hand uses an o-ring pressed between the seat and reg body and another between the HP cap and reg body. In recent years this has changed from an traditional round profiled o-ring to larger and more square profile ring that seals the gap between the seat and carrier as well as the carrier and reg body. This makes the cap o-ring largely redundant.

The Mk 10 piston uses a knife edged hard seating surface on the piston and the original HP seats were flat. However the current seats are now concave and generally similar in function to the Mk 15, 20 and 25 seats.

SP had some significant problems with seat life on the Mk 10 Plus and I believe some of the seats were subject to a recall. I initially converted a couple of my Mk 10's to Mk 10 Plus status when they first came out, but I converted them back after about half a season as the seats were failing prematurely. I recently converted one back to Mk 10 Plus status as an experiement as the current Mk 10 Plus seats and seat materials seem to be holding up much better.

I have never noticed a performance difference between the two although theoretically the Mk 10 Plus should offer a higher flow rate. But it's a case of you don't notice the improvement as the Mk 10 had enough flow rate already. It's a lot like having a car that will do 140mph when all the faster you ever go is 80 mph on the interstate anyway.

Your reg has two problems from what you describe - one being a faulty seat o-ring and the other being a worn HP seat. The leaking seat is a wear issue, not a design issue and in my experience the Mk 10 still has better seat longevity than the Mk 10 Plus.

As for the Plus upgrade being "recommended", I have never heard that. The upgrade is available and does increase flow rate a bit, but there was never any need or recommendation for divers to upgrade their Mk 10's. Any alledged recommendation has a lot more to do with suggestive selling than with a need to improve regulator performance. And again if you are more concerned with reliability and seat life, the Plus upgrade makes no sense in my opinion and experience. I think it is significant that the rounded seating edge piston design was discontinued on the Mk 20 and that SP returned to the knife edged piston design for the late production Mk 20 and Mk 25. This makes the Mk 10 Plus the only first stage to still use that design. If anything, I would probably consider converting a Mk 10 Plus to MK 10 status rather than the other way around.

Another benefit with the original Mk 10's is that SP has recently begun including 3 seats in the annual service kits. This allows a greater range of intermediate pressure adjustment with or without shims as desired and in some cases keeps the IP from exceeeding the upper limit in some older Mk 10's with springs that appear to be getting stiffer with age. The Mk 10 Plus seat design does not allow for different seat heights and an IP that is still excessive after all the shims have been removed can only be fixed by replacing the spring.

So in short, my advice is to stick with the Mk 10 configuration and pass on the upgrade. The basic seat and piston technology on the Mk 10 may be stone age, but it is time tested, bullet proof and utterly reliable - great qualities in a first stage.

The Mk 10 is one of the most venerated designs around,has a legendary reputation for performance and reliability and still has a dedicated following despite being out of production for over a decade. A lot of divers feel that SP has went downhill in first stage design in some respects since they replaced the Mk 10 with newer models. Personally, I think if SP reintroduced a Mk 10 "Classic" they would sell a ton of them. That probably won't happen though as it would steal sales from both the Mk 16 and Mk 25.

 

[omeko]

The Mk 10 on the other hand uses an o-ring pressed between the seat and reg body and another between the HP cap and reg body. In recent years this has changed from an traditional round profiled o-ring to larger and more square profile ring that seals the gap between the seat and carrier as well as the carrier and reg body. This makes the cap o-ring largely redundant.

Ahum. On the drawing it says 'washer' for the ring between the carrier and the reg body so when I took out the hard square ring I thought this was it. Turned out it was just a totally distorted and dried out o-ring.
I replaced it with one of those above mentioned 'traditional round profiled o-rings' and the leaking is over now. :11ztongue
The IM pressure is coming up a bit slowly but I guess that will probably settle itself with wear.

If anything, I would probably consider converting a Mk 10 Plus to MK 10 status rather than the other way around.

Everything really WAS better in the old days!

Another benefit with the original Mk 10's is that SP has recently begun including 3 seats in the annual service kits. This allows a greater range of intermediate pressure adjustment with or without shims as desired and in some cases keeps the IP from exceeeding the upper limit in some older Mk 10's with springs that appear to be getting stiffer with age.
The Mk 10 Plus seat design does not allow for different seat heights and an IP that is still excessive after all the shims have been removed can only be fixed by replacing the spring.

IP is a bit low; about 8.5 Bar while I've seen 9 - 9.5 recommended - though this specification may have been meant for newer versions.
I'm not worried about it really.

What does worry me about this 1st stage is the way the swivelhead is attached to the reg body; it's a mess inside really. On one side there's just two turns of thread and as a whole the thread doesn't look very solid. If your tank would topple and land on the swivel I think it would probably come off and impressively illustrate the high flow capacities of this first stage.

The Mk 10 is one of the most venerated designs around,has a legendary reputation for performance and reliability and still has a dedicated following despite being out of production for over a decade. A lot of divers feel that SP has went downhill in first stage design in some respects since they replaced the Mk 10 with newer models. Personally, I think if SP reintroduced a Mk 10 "Classic" they would sell a ton of them. That probably won't happen though as it would steal sales from both the Mk 16 and Mk 25.

The good news is I found another one in equal good state on the web for $70 and it's coming in tomorrow. It has the Stone Age black console with the depthgauge on the opposite side as well.
Oagh it's gonna look neat under the christmas tree with all the little lights reflecting... :dazzler1:

The next step is gonna be to find me a rubber drysuit and then I'll just start a new phenomenon called 'retro diving'. And in the process... why not make it a new forum on this board? I can picture it: RETRO DIVING 'Doing it cheap, doing it yourself and letting it shine'.

Cheers,

Marko

 

[DA Aquamaster]

8.5 bar if fine for the IP as it is squarely in the middle of the operating range. 9.5 bar would be the upper end and while it would allow a slightly higher flow rate, it also puts a greater adibatic cooling load on the first stage in cold water. Personally, I tend to set mine up in the lower half of the range and at or below 130 psi anyway.

The needle on the IP gauge should drop about 20 psi on an inhalation (and approx 30 psi with the purge button depressed) and then swing quickly back up to the max IP where it should lock up solidly with no creep at all. If it creeps at all after it swings, the issue is a worn HP seat. If however, the IP is coming up slowly, the needle is swinging slowly, or the IP drop is excessive, it could be a clogged filter.

The new style flat washer is red in color and has a lot more bulk than a conventional o-ring.

The concern with the swivel cap has been around as long as the Mk 10 - longer actually as the same concern was expressed with the swivel cap on the Mk 5. In fact Scubapro introduced the Mk 9, which was a MK 10 with fixed ports, to address this concern, but they did not sell many of them.

In practice as long as the hard plastic washer is used behind the swivel retaining nut to prevent excessive play and as long as the nut itself is not over torqued, there is no problemn with the swivel cap. I have never heard of one actually breaking off even when abused so I think it's a case of it being a lot stronger than it looks.

I think the retro diving concept works - it would be not quite vintage diving using all the regs that are 10-20 years old that work as good as and in many cases better than new models.

 

[omeko]

Personally, I tend to set mine up in the lower half of the range and at or below 130 psi anyway.

Drop is about 20 max and comes fiercely back at 120 and slowly drops to 110. Doesn't drop any lower, though. Currently no bubbles anywhere.

The concern with the swivel cap has been around as long as the Mk 10 - longer actually as the same concern was expressed with the swivel cap on the Mk 5. In practice as long as the hard plastic washer is used behind the swivel retaining nut to prevent excessive play and as long as the nut itself is not over torqued, there is no problemn with the swivel cap. I have never heard of one actually breaking off even when abused so I think it's a case of it being a lot stronger than it looks.

Hope so!

I think the retro diving concept works - it would be not quite vintage diving using all the regs that are 10-20 years old that work as good as and in many cases better than new models.

Couldn't agree more. Don't believe the hype!

 

[redacted]

Drop is about 20 max and comes fiercely back at 120 and slowly drops to 110. Doesn't drop any lower, though. Currently no bubbles anywhere.

I run my Mk10 in the 120 to 130 range. When I purge the second, the IP drops to aronund 90 psi. With normal breathing, the drop is not quite that much. Once it has recovered from the IP drop and lockup up, there should not be any further drom in IP unless you initiate it or you have a leak somewhere. I'd take that back to the bath tub and find out where the IP drop is coming from.

 

[omeko]

I'd take that back to the bath tub and find out where the IP drop is coming from.

The bloody IM pressure gauge...!

 

[DA Aquamaster]

That makes sense as an IP drop of 10 psi after the lockup is really, really strange.