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MK5 HP Seat

Discussion in 'Vintage Diving & Equipment' started by Art Challacombe, Jul 25, 2021.

  1. Art Challacombe

    Art Challacombe Registered

    # of Dives: I just don't log dives
    Location: Hawaii
    27
    42
    Aloha everyone,
    recently I purchased a nice looking MK5 first stage on an auction site. Upon receiving it, I checked the IP and it had a creep up to around 148 psi. Feeling it was too high, I proceeded to tear it down for a rebuild. To my surprise, the white HP seat face was flat as opposed to the normal concave configuration. So, I replaced it with a Scubapro -1 seat, rechecked the IP and after recycling the IP had a final lock up at 128 psi which is fine with me.

    I’ve never seen a flat HP seat in a MK5, so my question is; is this seat correct for Scubapro regulators? Other than not having the concave face, it fits the HP carrier perfectly and looks new. There is no number or markings on the seat. Any ideas?
     
  2. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    6,001
    7,875
    Lots of flat inexpensive aftermarket seats around. They match the original flat Mk5 seat, which was discontinued after the cone seats were introduced.
    But your flat seat isn't "wrong". Another possible cause of your IP creep is an imperfection in the knife edge. The cone seats are more forgiving of that.
     
    AfterDark likes this.
  3. Art Challacombe

    Art Challacombe Registered

    # of Dives: I just don't log dives
    Location: Hawaii
    27
    42
    Thanks rsingler, that makes sense to me. Fortunately, the previous IP creep was not from the piston. I checked the knife edge with a jewelers loop and the edge is perfect. Also, I left the the regulator on a full tank overnight. It read 125 psi last night and today it’s at 128. I’m satisfied with those numbers.
     
    AfterDark likes this.
  4. Art Challacombe

    Art Challacombe Registered

    # of Dives: I just don't log dives
    Location: Hawaii
    27
    42
    I’m guessing that perhaps the seat face had not had not been cycled enough to create a permanent lock. To be fair, the initial IP was at 138 and creeped up to 148 after a couple of hours. Maybe I should have been more patient and cycled the regulator as Pete Wolfinger says.
     
    AfterDark likes this.

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