Scubapro O-ring Sizes

[V&G]

Curiously, looking in TSS by products, posted here, I see that almost for all sizes used EP85 except for 010, used with EP70..

 

[V&G]

TSS for MK25:


MK25-MK20 Trouble Shooting Guide:


S600-S550 Trouble Shooting Guide

 

[Zung]

Sometimes it makes sense, sometimes it doesn't.

In the MK20/25, all the HP o-rings are EP85, the IP o-rings are EP70, with the exception of the piston crown o-rings which are EP80, but EP70's work well there.

In the G250V, the Venturi and the jam nut o-rings are EP85 fo no good reasons, I'm sure EP70's work, even though I've never messed with the Venturi lever.

Another way to find out for sure is to ask if somebody has done it before, then wait a while and ask again if that somebody is still alive.

 

[Iknee]

V&G

I like your trouble shooting guides... What other ones do you have?

 

[V&G]

Sorry, I don't have others. Just found them on the net and saved some relevant for me.
I found them here. Hope you'll find what you'r looking for. Let me know, if you need some help with it..

 

[redacted]

I thought those and other Scubapro Troubleshooting Guides were a bit on the trivial side. The fact that Scubapro thought they were necessary and appropriate for their trained shop techs speaks poorly of their standards. They encourage semi-mindless parts replacement rather than good diagnostics based on a thorough understanding of regulator design and function.

 

[Zung]

There were some uncertainties regarding the 2 tiny o-rings that go between the S-Wing poppet and the balance chamber of the balanced second stage.

I just did a side by side (sort of) comparison between the 2.2mm x 1mm original o-rings and the 2.5mm x 1mm Viton o-rings I got from McMaster.

While the 2.2mm ones go straight in, the 2.5mm ones do require a bit of wiggling before they agree to go in the balance chamber, especially the first one.

Once they fit, they all appear to work alright: the 2.5's go to a 156, and the 2.2's go to a G250, and both regs are in the 23mm/.9" range.

If I had a choice, I'd go with the 2.2x1mm.

 

[Zung]

Mystery solved.... maybe.

Master couv has previously measured the groves (journals) of the S-wing poppet:

• Active journal (near the balance chamber): .091"/2.31
• Wiper journal (near the LP seat): .077"/1.96mm

I measured an older poppet, the blue one with the metal stem and a single o-ring, and:

• Single journal: .0962/2.44mm

So now it makes sense... sort of:

• The current all plastic S-wing poppet with a smaller journal takes a 2.2mm, with a 5% strech
• The older poppet with the metal stem and a larger journal takes a 2.5mm, with a 2.5% oversize

 

[Couv]

Brother Zung,

That makes absolute sense. Someone posted an older reference that showed a 2.5mm in that application. It was probably for the older balance poppet with the metal stem.

c

 

[dpwheeler]

Well I just bit the bullet and bought all the sizes for a MK10 - EDPM. If anyone wants a set e-mail me - Dave@dasalinc.com - and I will sell you 2 sets for $10.00. That will give you enough for this and your next overhaul. I doubt I'll live long enough to use 100. If you just need one or two I'll be glad to help you out. Just let me know.
DW