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Maybe you could try hieroglyphics, the shop obviously did, anything in the dead sea scrolls?
Scubapro MKV piston recall?
- Thread starter Goatman1225
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Maybe you could try hieroglyphics, the shop obviously did, anything in the dead sea scrolls?
halocline
Contributor
I’ll go through your points one at a time. I’m very familiar with MK5s. If you want to post a photo, especially of the piston, I’ll be happy to comment on that. But the bottom line is that I think the guy at the shop doesn’t really know what he’s doing with this regulator and of course both the shop and SP are in business to sell new regulators.
First, the 5 port MK5 is, in my opinion, one of the best 1st stages ever. I have had them go for 5-6 years between rebuilds and hold IP perfectly. I’d be happy to look at your piston, but I’ve never seen an early piston in a 5 port MK5. Not impossible, but I suspect either this guy at the shop doesn’t recognize the piston for what it is (even the later ones look different from subsequent pistons on the MK10-15-20/25) or someone put an earlier piston in your regulator. Either way, it’s very easy to find good MK5 piston on the used market. Of course a shop won’t do that, and you can’t blame them. It’s not their business. I would have to see that piston, but I’m very skeptical that it actually constitutes any sort of risk whatsoever.
Second, the spring. They do, on occasion, wear out. But there are three seats that come with the MK5/10 rebuild kits, and the shortest seat (marked + on the back) is the one to use to raise the IP. I keep my MK5s between 125-130 PSI, which works perfectly. Higher IP is not advantageous, especially with a balanced 2nd stage. If your regulator won’t get to 125 with the + seat and a shim at each end of the spring, then you do need a new spring, and once again, the used market is perfect for this.
Third, the o-ring that seals the HP seat is correct; all MK5s used an o-ring in that spot. Later, in the MK10, it was replaced by a square-profile washer, which works great, but the issue with the o-ring was that it wasn’t idiot proof enough for poorly skilled or trained techs. (It takes a little patience to seat that o-ring) The fact that your guy thinks this o-ring was ‘red-necked in’ is an indication that he isn’t very familiar with this 1st stage. It’s not uncommon for dive shop techs to lack any sort of understanding of older regulators.
Fourth, I have seen some 109 diaphragms get sticky, which is an indication that the silicone is breaking down. Fortunately the G250 diaphragm fits and works perfectly, and there are plenty of those around.
If you want a new regulator, go for it. This is a hobby, and spending your money on your hobby is definitely your business. But you’re not getting expert knowledge on your regulator. Here’s a short story; I once walked into my local scuba pro shop when I lived in San Antonio, maybe 15 years ago, and saw a bucket of 109s and Air1s at the foot of the dive shop tech’s bench. He was going to throw them away after having sold new regulators to customers that had brought them in for service. So I bought the bucket for $100, and still use 3 of those 109s for SM, stages and deco regs. (They are perfect for high FO2 use)
I’m tempted to offer you a small amount of money for your MK5/109 and rebuild it and add it to my collection, but I have plenty! Still, if you do end up getting a new regulator, and you want to responsibly get rid of yours, I’ll take it, rebuild it, and post photos on here. I probably have a donor spring if it’s needed, and I’m sure I could find the other parts. But again, rsingler would be a good guy to talk with because he knows these old regs and he’s in the business of rebuilding them. He’s on this forum frequently.
One last word to an already-too-long post. I’m not a huge fan of the MK19, although in fairness it’s been years since I’ve even seen one or worked on one. But my memory is that they are not very well balanced; IP rises about 10 PSI (or more) as the tank empties. With a balanced 2nd stage this doesn’t really matter, but I’m a stickler; IMO the first stage has one job to do, provide constant, steady IP to the 2nd stage. I wouldn’t spend real money on a 1st stage that does not do that. I don’t know much about the D420, but I have heard that it’s nothing like the older D series regs that I love and have several of.
axxel57
Contributor
The SP MK5 1st stages founded SPs reputation as leading scuba regulator manufacturer in the 60ties and 70ties.
Since its introduction in 1965 (resp. 1966) it was sold in high numbers world wide.
In Europe (maybe also in the US), it was sold still in 1987, so years after the introduction of the MK9/10, which I find remarkable……
Until 1978 the MK5 had only two LP Ports, then four, and from 1981 on five LP Ports.
I have quite a lot of MK5 1sts (2-4-5 LP Ports), parts, and some MK1-6-7-8, but I found it always difficult to find specimens with the newer type of piston.
But maybe that’s not so surprising, since the ‘newer’ MK5-1-6-7-8 Piston was introduced quite late in 1983 and came quite sure only 1984 on the market, so if one didn’t actively look for a change of his piston, he/she got it only if it was purchased 1984 or later (don't know how long those pistons were available).
Maybe in the US divers got those new pistons more often offered, here in Europe almost all of the DIN MK5s have still the old configuration, what was and is technically no problem, latest since the Cone HP Seat was introduced in 1987/88…….
Attachments
Thanks for the post and in particular for the copy of the engineering bulletin.
It is interesting the explanation for why the piston change. According to the explanation, "the high pressure seat can now be reversed allowing both sides to be used".
IMHO, they went through a lot of trouble with a new piston to be able to reverse the seat, something no dealer would have done.
Scubapro was not going to admit to the issue of the piston getting embedded into the seat. I have no idea how often that happened. It must have been very rare, but even only once is too many. I never saw it happen. As far as I know that became a non-issue with the new seats. Therefore, the old pistons are supposed to be perfectly fine with the new seats, that are now available.
A piston embedding itself into the seat would be almost as catastrophic (but not as spectacular) as having the swivel bolt on a MK-5 break off in the middle of a dive...
halocline
Contributor
I’m always amazed by the level of detailed understanding by Axxel and Luis. You guys are true experts.
That said, I’ve certainly never had a problem with the MK5 turret retainer bolt. Most of mine have been replaced by the SS bolts that Bryan had machined, but I still have one or two brass ones. It’s my understanding that the risk of failure was due to some techs grossly overtorquing the brass bolts, damaging the threads. I’ve seen some early MK5s used a simple circlip to fasten the 2 port turret. Maybe that’s as strong or stronger than the bolt, but it doesn’t look it!
Anyhow, has anyone on this board ever actually experienced a MK5 turret bolt break during a dive? And I’m trying to figure the actual force pushing the turret off the regulator body. Is it IP times the area of the interior of the turret bolt?
That said, I’ve certainly never had a problem with the MK5 turret retainer bolt. Most of mine have been replaced by the SS bolts that Bryan had machined, but I still have one or two brass ones. It’s my understanding that the risk of failure was due to some techs grossly overtorquing the brass bolts, damaging the threads. I’ve seen some early MK5s used a simple circlip to fasten the 2 port turret. Maybe that’s as strong or stronger than the bolt, but it doesn’t look it!
Anyhow, has anyone on this board ever actually experienced a MK5 turret bolt break during a dive? And I’m trying to figure the actual force pushing the turret off the regulator body. Is it IP times the area of the interior of the turret bolt?
The pressure thrust pushing on the swivel turret is almost insignificant. Yes, "pressure thrust", is pressure times the area. The pressure is only the IP and the area is also small.
That is why the snap ring was just fine to hold the pressure thrust. Shearing the snap ring was not going to happen, but the bolt seemed like a better idea. But, it is debatable...
There are two other loads to consider, mechanical abuse (lifting the tank kit from the hoses on the turret) and the torque on the bolt. The torque (or tightening the bolt) is what keeps the bolt from unintentionally loosening what the swivel rotates. So the minimum torque and the maximum torque become a balancing act.
The area on this bolt (in brass or stainless) does not allow a lot of room between the minimum and the maximum. I did the calculations before I did the drawings for Bryan. I will share them later. I am heading out in a few minutes to my LDS to help her with some regulators.
The issue is that if the bolt has been over-torqued it is very hard to detect a flaw. A minor flaw is probably not an issue with the pressure thrust, but the handling loads from the hose pulls from different directions is very unpredictable. That is even if you are very careful, the hose fitting have a lot of mechanical advantage up and down on the turret.
My preferred solution (in theory) would be to use some mild rubbery locking compound to avoid twisting and unscrewing the bolt and keeping the torque in the low end.
I have never seen this failure in person, but I remember seeing a video underwater, that I cannot find. It was very impressive (maybe I imagined it).
The failure is much more likely to happen during service, but in the link below it happened during a ditch and don drill, which makes sense.
I shared my drawing in that thread (page 3).
That is why the snap ring was just fine to hold the pressure thrust. Shearing the snap ring was not going to happen, but the bolt seemed like a better idea. But, it is debatable...
There are two other loads to consider, mechanical abuse (lifting the tank kit from the hoses on the turret) and the torque on the bolt. The torque (or tightening the bolt) is what keeps the bolt from unintentionally loosening what the swivel rotates. So the minimum torque and the maximum torque become a balancing act.
The area on this bolt (in brass or stainless) does not allow a lot of room between the minimum and the maximum. I did the calculations before I did the drawings for Bryan. I will share them later. I am heading out in a few minutes to my LDS to help her with some regulators.
The issue is that if the bolt has been over-torqued it is very hard to detect a flaw. A minor flaw is probably not an issue with the pressure thrust, but the handling loads from the hose pulls from different directions is very unpredictable. That is even if you are very careful, the hose fitting have a lot of mechanical advantage up and down on the turret.
My preferred solution (in theory) would be to use some mild rubbery locking compound to avoid twisting and unscrewing the bolt and keeping the torque in the low end.
I have never seen this failure in person, but I remember seeing a video underwater, that I cannot find. It was very impressive (maybe I imagined it).
The failure is much more likely to happen during service, but in the link below it happened during a ditch and don drill, which makes sense.
I shared my drawing in that thread (page 3).
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