You may have run across that really irritating whine in your Mk25, and Scubapro has long fought that issue with a variety of trial fixes.
But until today, I had NEVER run across it in a Mk10. Just finished a standard overhaul and used an OEM Service kit 10.500.045, two shims and a -| seat for the repair. Locked up right at 135 with no creep, and I was happy until I breathed from the second stage.
A loud, high-pitched whine sung out, and I thought, WTH? There's no stack spring in the HP gas pathway to vibrate! So I did the other Mk25 fixes: I greased up the the o-ring and piston shaft with extra lube. I rotated the HP Seat 180°. Nothing helped. At 500 psi, the whine was almost gone, but at full tank it was unbearable.
To digress, in the old days, that purple .147 o-ring would rarely buckle and your HP seat carrier would bubble away.
The same problem exists with the 2-013 that folks use when they make up aftermarket kits. It's not common, but it happens.
Well, Scubapro made a switch somewhere around '98-'99 to that orange plastic washer, and they've stuck with it.
Well, here's what I think was happening today. I think the square edge of that washer, for some reason in that high-flow gas pathway, was acting like the mouthpiece of a flute. Because of the problem of that thinner o-ring in the old days, I'd been using a metric 10x2mm duro 90 oring in my aftermarket kits. So I stuck one in this reg, even though I was a little unhappy about deviating from an OEM kit for a customer.
And when I switched that 10x2 in, in place of the plastic washer, things were completely quiet. I think the rounded surface smoothed out the flow.
I'm learning new stuff every year. I thought I had the Mk10 down pat after all this time...
But until today, I had NEVER run across it in a Mk10. Just finished a standard overhaul and used an OEM Service kit 10.500.045, two shims and a -| seat for the repair. Locked up right at 135 with no creep, and I was happy until I breathed from the second stage.
A loud, high-pitched whine sung out, and I thought, WTH? There's no stack spring in the HP gas pathway to vibrate! So I did the other Mk25 fixes: I greased up the the o-ring and piston shaft with extra lube. I rotated the HP Seat 180°. Nothing helped. At 500 psi, the whine was almost gone, but at full tank it was unbearable.
To digress, in the old days, that purple .147 o-ring would rarely buckle and your HP seat carrier would bubble away.
The same problem exists with the 2-013 that folks use when they make up aftermarket kits. It's not common, but it happens.
Well, Scubapro made a switch somewhere around '98-'99 to that orange plastic washer, and they've stuck with it.
Well, here's what I think was happening today. I think the square edge of that washer, for some reason in that high-flow gas pathway, was acting like the mouthpiece of a flute. Because of the problem of that thinner o-ring in the old days, I'd been using a metric 10x2mm duro 90 oring in my aftermarket kits. So I stuck one in this reg, even though I was a little unhappy about deviating from an OEM kit for a customer.
And when I switched that 10x2 in, in place of the plastic washer, things were completely quiet. I think the rounded surface smoothed out the flow.
I'm learning new stuff every year. I thought I had the Mk10 down pat after all this time...
