Regulator Geeks: Scubapro Mk19EVO - teardown & discussion

[rsingler]

Okay, you've won me over. I got a loaner S620Ti from the dive shop. The S270 has arrived.
We'll talk about technopolymer barrels vs metal (and the same for the orifices, for that matter).
Haven't been able to find an old S550, but there's a G250HP with the same tuning knob and case size that will fit the discussion of purge volume.
Head on over to Regulator Geeks, Part II
and watch for Zoom sign-on info in the next few days...

 

[datth]

I know someone in San Francisco with an unserviced Mk16 who wouldn't mind having it serviced for free if you're interested in demo'ing that in Part II, @rsingler

 

[rsingler]

Lol, sorry! Second stage discussion only, this time!
Now if you had an S550, I might be tempted to send it back with that serviced Mk16...

 

[datth]

Lol, sorry! Second stage discussion only, this time!
Now if you had an S550, I might be tempted to send it back with that serviced Mk16...

Ha ha, unfortunately that friend's Mk16 comes with the G250HP, if that interests you.

 

[rhwestfall]

I'm leaning toward: "What was old is new again"...

 

[mictrik]

Does anyone have an explanation on the reason for which the original MK19 had limited succes in the US?

I don't believe it ever appeared In the US Catalogue. I personally believe that their marketing wanted to stick with the MK-25 as their premier first stage given their balanced piston heritage. The MK-19 with it's turret takes away an obvious distinction the MK-25 had from the MK-17. Now with the introduction of the MK-19 EVO it seems that Scubapro was ready to have it share lead role with the MK-25 worldwide. They are both superb performers providing very high flow rates with almost no change in IP as HP pressure source decreases.

 

[Pressurehead]

Old topic, well not that old.
Here in Oz the Scubapro Mk19 EVO is cheaper than a Mk 17 [only $4] and $74 cheaper than a Mk25 EVO, and only $75 dearer than a Mk 11.
They were "all the rage" when they hit the market, I just might buy one for the hell of it now [or not].
What's another regulator 'between friends'.
I don't own a "environmentally sealed first stage".

 

[halocline]

They are both superb performers providing very high flow rates with almost no change in IP as HP pressure source decreases.

I assume that the MK19 is the same as the MK17 but with the addition of a turret. If that's correct, then my experience is that the MK19 would have a much wider IP swing as tank pressure decreases than the MK25, although it's in the opposite direction due to being an upstream valve. Every MK17 that I've worked on has an IP swing of almost 10 PSI over tank range; i.e if it's 125PSI at 3000PSI, then at 300 PSI it's close to 135PSI. So unless they've changed something in the balance chamber/poppet/orifice arrangement, then the same would be true of the MK19. It's only partially balanced. The MK20/25 in my experience is very good with regards to keeping consistent IP across the supply range, only dropping a couple of PSI.

How much this matters with a balanced 2nd stage is questionable. Probably not noticeable at all to most divers. As you mentioned, they're both excellent 1st stages. I routinely dive with MK5s and 10s, in pretty demanding situations, and they are also only partially balanced in practice. I think this is primarily due to increased clearance between the body and HP o-ring which allows a bit of increased friction at high supply pressures and pushes IP up 7 PSI or so (more on the MK10, a little less on the MK5) at full tank pressure.

 

[Geo7]

Here are some data from the MK19 Regulator Geek Video, where Rob compares the IP swing of various 1st stages from full to empty tank (starting at around 56 mins into the video). The results are shown at 104 mins (screenshot attached below).

The Mk17 has a an 8 PSI swing and the Mk19 Evo 4 PSI. Apparently tolerances in hard parts and o-rings were modified.

Anyway, I do agree with your conclusions and like your reg selection

 

[L13]

Here are some data from the MK19 Regulator Geek Video, where Rob compares the IP swing of various 1st stages from full to empty tank (starting at around 56 mins into the video). The results are shown at 104 mins (screenshot attached below).

The Mk17 has a an 8 PSI swing and the Mk19 Evo 4 PSI. Apparently tolerances in hard parts and o-rings were modified.

Rob retested after someone questioned the numbers, and both the Mk19 Evo and Mk25 were less than 2PSI. I just watched all the videos on Rob's YouTube channel