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Post by scubalawyer on Jan 22, 2020 9:03:00 GMT -8
New in box MR12. It will probably work just fine but I'm gonna tear it apart anyway. Any idea what year it is?
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Post by SeaRat on Jan 22, 2020 12:59:55 GMT -8
Super nice, and I would say this one is mid-1970s.
John
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Post by nikeajax on Jan 22, 2020 13:21:49 GMT -8
I think John is right, I'm gunna say 1973-4, just because! When did they change to the bull's-eye on the purge buttons?
As for a tear down, I totally agree there and please be sure to get a new second stage diaphragm for it: those friction plates can and will delaminate.
BTW, if you ever get an original HW Scuba, the second stage MR-12 diaphragms make a really dandy replacement exhaust diaphragm for them.
JB
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Post by SeaRat on Jan 22, 2020 17:55:46 GMT -8
I think that the MR-12 diaphragm has a riveted, stainless steel friction plate for the second stage diaphragm. They are pretty much indestructable, but tend to harden with age, and not be so flexible. The very new ones actually fit (from the MR12-II and MR12-III are a very flexible neoprene or silicone, and so would improve the performance of the MR12. Here's the original AMF Swimaster7 datasheet for the MR12: AMF Voit MR-12 Sheet001 by John Ratliff, on Flickr MR-12 Spec Sheet002 by John Ratliff, on Flickr IMG_1267 by John Ratliff, on Flickr You will note that I have exchanged my exhaust mushroom valve for a like one made of silicone too. So far as the date of your regulator, looking at the serial number I'd say it was toward the end of the MR12. The 1972 AMF Voit catalog does not show the MR-12, but shows the V124 Viking I Regulator (with a MR12 forst stage and a earlier (Conqueror II or Avalon III secand stage). The 1973 AMF Swimaster Professional Diving Equipment catalog has the MR-12 in it. So I'd put the MR12 start at about 1973. The AMF Voit Swimaster Professional Dive Gear and Recreational Swim Equipment catalog for 1979 has both the MR12 (not pictured, but listed) and the MR12-II. About the MR12, Voit states, "Proven superiority - the first single-hose unit approved for use by the U.S. Navy..." So I think the MR12 ran from 1973 to 1979, before the next generation came out. Since your serial number is fairly high, I'd feel that it was closer to 1979 than 1973. By the way, I'd surely like to have been with the AMF Swimaster people when they shot the 1973 catalog at Truk Lagoon, but I was pretty overwhelmed with my studies at Oregon State University and my committment with the USAF Pararescue for the 304th Aerospace Rescue and Recovery Squadron (Reserve). The catalog shows divers on the wrecks in Truk Lagoon. John
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Post by scubalawyer on Jan 22, 2020 18:17:04 GMT -8
Hi John, do you happen to have the MR12 Spec Sheets in .pdf form?
Mark
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Post by herman on Jan 22, 2020 18:18:15 GMT -8
Mark, the Mares Abyss diaphragm is a perfect fit for that second stage and is available from Mares dealers. The first stage requires a pin spanner to remove the HP assembly, I make one for it.
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Post by SeaRat on Jan 22, 2020 18:26:52 GMT -8
Hi John, do you happen to have the MR12 Spec Sheets in .pdf form? Mark I do now. I had them as jpg images, but I've now exported them to pdf. I can send them to you if you PM me your e-mail. JB, Swimaster didn't get rid of the bullseye on their second stage, that became their new look in 1979 (according to my catalog). The Polaris II, MR12 and MR12-II all had the bullseye purge button in 1979. Earlier is what Mark has. Below I'm diving my MR12-II with the bullseye second stage. John with Scubapro mask and MR-12II by John Ratliff, on Flickr John
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Post by scubalawyer on Jan 22, 2020 18:42:40 GMT -8
Mark, the Mares Abyss diaphragm is a perfect fit for that second stage and is available from Mares dealers. The first stage requires a pin spanner to remove the HP assembly, I make one for it.Hmmmm... shameless self-promotion. I love it! If my adjustable spanner don't work I'll hit you up for one. Thanks for the tip on the diaphragm.
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Post by nikeajax on Jan 22, 2020 18:47:10 GMT -8
I just use a small needle-nose pliers on mine, worked great too!
JB
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Post by herman on Jan 23, 2020 3:37:28 GMT -8
The assembly sets a little deep in the hole so getting a spanner on it can be difficult, the angle is off. As for using pliers, you can get away with it some times but if it's tight or corroded you end up damaging it. No sense damaging it using improper tools when the correct ones are available. The tool also works on Voit Titan and Trieste as well.
A word of caution. The HP seat for the regs that used that HP assembly (MR-12,Titan,Trieste) came in 2 different versions. The depth of the hole in the seat and the pin length are different and they can not be mixed. Later service kits came with a new pin and there is no telling which that one has. If you use a new seat, be sure to check the depth of the hole to make sure you have the correct pin length. Modern USD/AL seats will work if you have the correct pin. Like other USD and Voit regs, the spacing between the HP seat and pin pad should be in the 0.040 range and pin pad should bottom out leaving no space under it when pressed in. If you don't have the correct pin, drop me an email, I have some suitable material to make them. The material must be hardened so stuff like nails or brass rod will not work.
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Post by george on Jan 23, 2020 4:45:44 GMT -8
Were can you get or is there a crossover for the second stage diaphragm?
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Post by nikeajax on Jan 23, 2020 9:25:08 GMT -8
...A word of caution. The HP seat for the regs that used that HP assembly (MR-12,Titan,Trieste) came in 2 different versions... Herman, thanks for the reminder! On that note: Mark and anyone else, the OEM seats for these don't hold up through time/age: the material used can and will become brittle. What my personal experience was, was that the tank pressure will crack the material and quickly blast the soft seat to pieces. I would strongly suggest replacing the seat and push rod: USD seats won't do this. Anyway, just thought I'd mention it JB
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Post by herman on Jan 23, 2020 10:22:24 GMT -8
Were can you get or is there a crossover for the second stage diaphragm? See above , the Mares Abyss works perfectly and is (or at least was recently) currently available at any Mares dealer...assuming you can get them to sell you parts.
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Post by scubalawyer on Jan 23, 2020 10:39:16 GMT -8
Stooopid question time for me. The schematic for the MR12 says its a "pressure balanced first stage." The recommended IP range is 120-135 psi. I do see springs on both sides of the seat but an unbalanced AM seems to have the same thing. Is it really balanced so that I can adjust the IP on any pressure tank, or do I need to adjust IP on a 300-500 psi tank like on an AM?
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Post by cnotthoff on Jan 23, 2020 11:14:49 GMT -8
SL,
It's all about part #4 in the schematic John posted. US Divers calls it a balance chamber. That chamber puts tank pressure on both sides of the HP seat, so that whatever pressure is in the tank, it's BALANCED. The springs are there in any diaphragm 1st stage. Pistons have springs too.
I adjust the IP at full pressure, but always like to check it at around 300-500 psi as well.
Good Dives, Charlie
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