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Amphos Air - serial O ring ‘blower’

Discussion in 'Sherwood SCUBA' started by Dough18, Feb 15, 2019.

  1. Dough18

    Dough18 Angel Fish

    # of Dives: 500 - 999
    Location: USA
    14
    3
    3
    Hi All

    Apologizes if a duplicate thread. I am in Roatan and internet won’t allow searches easily.

    Have an SR first and second stages. Recent added an Amphos air transmitter. I keep blowing the transmitter O rings. Twice over Xmas in Grand Cayman. Twice here. Everything was serviced recently (Oct 2018). Tried a heavy gauge O ring with no success. Certified Techs doing the work.

    Anybody have any ideas what the problem might be??? Furtrating...
     
  2. JackD342

    JackD342 Dive Shop

    # of Dives: 500 - 999
    Location: Highland Park, IL
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    When you say Certified Techs are doing the work, what work is that? Someone is helping you troubleshoot providing a second set of eyes and a second opinion? Or just describing who has worked on your gear in the past and installed the transmitter the first time? Also, can we assume you are referring to the o-ring at the HP port, and not the o-ring on the battery compartment?

    Unless there is something very unusual happening with the threads either on the transmitter or on the 1st stage, I can't think of anything from your description that doesn't strongly suggest some variation of "user error." (I am including any Tech who touched it in that user group.)

    Wrong o-ring? Not snug enough? Damaged o-ring? Accidental torquing of the transmitter after install?
    Are you removing and replacing the transmitter every time you travel or store your gear? Or just installed once and left alone?
    What do you mean by "heavy gauge" o-ring? If you used an o-ring thicker than intended, that could very easily extrude as the transmitter no long fully captures the entire cross section when snugged up, leaving exposed rubber to blow out.

    Sorry I don't have any answers, but maybe my questions will help.
     
  3. Dough18

    Dough18 Angel Fish

    # of Dives: 500 - 999
    Location: USA
    14
    3
    3
    Yes, the transmitter O ring at the HP port.

    The technicians are the repair folks trying to solve the problem. All have taken the transmitter off and then re-installed (three different people). One was the Sherwood rep who happened to be in the shop in GCM.
     
  4. chris kippax

    chris kippax Divemaster

    # of Dives: 500 - 999
    Location: Australia
    553
    320
    63
    Wrong duro oring?? Try a duro 90 and see if that helps
     
    rsingler likes this.
  5. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
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    A couple of thoughts...
    The SR has a chamfered land for the HP oring: 20190215_185056.jpg
    That means that whatever holds the oring in the well (port plug or transmitter), it has to completely cover the hole, or the oring will extrude more easily than with a vertical land.
    20190215_185624.jpg The Amphos Air transmitter has a mount which should provide complete top cover for the HP port, because it's clearly wider than the hole. My question is, how much wider?
    The reason I ask is that in the SR-1 at least (don't know about the SR-2), the trim cover is very close:
    20190215_185207.jpg 20190215_185145.jpg
    Note the little "ledge" of plastic next to the port. If the transmitter contacts that plastic trim, it may prevent the threaded portion from fully seating against the reg body. With ANY gap, extrusion of the o-ring over time is inevitable.
    As @chris kippax noted, make sure it's a duro 90 o-ring (try both a 2-011 and 2-012), and make sure you can see zero gap between the transmitter and body when you hold it sideways. If the plastic trim is keeping the transmitter from seating completely, it will be an easy matter to remove it, sand it flat at that location, and replace it. That will require removing the yoke retainer, so it may mean a visit to the shop if you don't service things yourself.
    My 2¢. Good luck!
     
    Dough18 likes this.
  6. JackD342

    JackD342 Dive Shop

    # of Dives: 500 - 999
    Location: Highland Park, IL
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    If you decide the trim piece is the issue and don’t want to modify it, you could also try adding a short hose or a small HP extension to stand the transmitter off a bit.
     
    Dough18 and rsingler like this.
  7. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
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    Frankly, I agree with Jack. I'm always afraid some boat crew is going to "help" me lift my rig and end up using the transmitter as a handle. There has been a thread or two on the subject, and it's uncommon, but I still dive with a short hose on my transmitter, "extra failure point" notwithstanding.
     
  8. herman

    herman Divemaster

    # of Dives: 500 - 999
    Location: Raleigh,North Carolina
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    I agree, double check that the transmitter is completely covering the opening with at least a tiny bit of overhang. There must be no gap between the reg and the transmitter. Inspect the transmitter and reg for any slight ding or gouge where they intersect. Also makes sure that the transmitter screws FULLY into the port hand tight. I have seen a hose that had a very slightly too long threaded section that was bottoming out in the port, preventing the underside of the hose connection from solidly joining the reg. If it extrudes again, mark the location on both parts with a sharpie, that way you can pay special attention to that area.
    You might also want to try a 3-904 oring in 90 durometer. That is the correct oring for this connection but most use the more common 011.
     
    Bob DBF, Dough18 and rsingler like this.
  9. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    2,874
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    If you can't get a 904, try a 2-012 duro 90.
    That is that closest O.D. match to the 904, and it's at the outside and top of the oring where the seal is being made (that 90° corner between the reg body and the roof formed by the transmitter mount). There may be no oring contact at all on the thread side, under pressure. There are a few companies that specify a 2-012, but I don't know what Sherwood's exact ring spec is.
     
  10. Scubagaskets

    Scubagaskets Nassau Grouper

    160
    34
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    If it any any help check my catalogue I got many strange sizes around that size. Catalogue - Premium O-rings Provider for Scuba Diving
     

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