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Cracking Adjustment

Discussion in 'Dive Equipment' started by Scottish Diver, Aug 11, 2017.

  1. Scottish Diver

    Scottish Diver New Member

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    Hi all,

    First proper post following intro so please go easy if this is a daft one!!

    I've recently picked up a new reg set - Scubapro mk25 evo with a700 2nd and R195 octo. They were purchased via an online authorised dealer and I did pay additional to have them set up / tuned correctly.

    Having done around 5 dives, I'm not convinced that this has been done correctly. I took them along to the pool last night for a try and I noted the following:

    • A700 cracking pressure seems too high - with Venturi on and resistance knob set to its lightest, the ref won't sustain a free flow when the purge is depressed.

    • cracking pressure - measured with a ruler from the front of the reg is 2 1/4 inches or just shy of 6cm - the water level is above he chrome writing just in front of the mouth piece by the time air is released.

    • It breathes noticibly harder when looking up towards the surface - bear in mind this was just in a pool so not deep.

    • I have had it down to 35m so far and it was ok, just seems like it should be a lot better?

    • R195 seems to do what could only be called a groan and the end of every inhalation. It's not throughout as you sometimes get when the reg is out of water - note that this is below the water as well.

    Any comments / hints or tips would be greatly appreciated. If it's something that really needs addressed by a dealer than any recommendations in the London / SE area would be good as I don't want to go through the process of sending back and forth to the original retailer.

    Thanks
    Chris
     
  2. jb2cool

    jb2cool Moderator
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    Were they brand new? If so you shouldn't have had to pay any extra to have them tuned.

    If you get it sorted by anyone else then you'll likely have to pay a servicing charge and that could be in the region of £80. I can't see a dealer doing it for free when it was bought elsewhere.

    When you are testing the freeflow, are you doing this in air or water? which way is the reg pointing? Wit hmine, I think in water, with the mouthpiece of the reg pointing up and venturi on, my reg freeflows on pressing the purge but if I turn the venturi off it doesn't. I don't recall what it does in air as I don't think I've tested it.
     
  3. Scottish Diver

    Scottish Diver New Member

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    Brand new yes.

    Surely the cracking adjustment should be quite straightforward with the correct inline adjustment tool? I'm obviously happy to pay a reasonable amount but as no real disassembly is required I would hope that it wouldn't be much!

    It won't sustain free flow above the surface in any direction.

    Thanks
    Chris
     
  4. jb2cool

    jb2cool Moderator
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    It can't hurt to ask a local shop to do this and see what they say. If you are South London and anywhere near West Norwood then Amphibian (http://www.amphibian-sports.co.uk/) are excellent.
     
  5. nickb

    nickb Active Member

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    +1

    There's no way you should have been charged extra to have brand new regs 'tuned'. The shop was taking the piss.

    Without an inline adjustment tool, all you need to do is take the hose off and turn the adjustment screw inside with a flat screwdriver. I'd suggest turning it anticlockwise about an 1/8th of a turn each time until you're happy with it.

    A correctly adjusted second stage should free flow when purged with the venturi knob in the 'Dive' position and not free flow with it in the other position.
     
  6. taino

    taino New Member

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    Chris,nice reg you bought.

    Problem is that SP usually is adjusting their regs on the conservative side of the specs, means harder than it would be possible, probably to avoid the regs free flowing after one or two dives (after the break in period).

    So it is a good idea to let the new 2nd be checked and fine adjusted by a technician.

    Since you have the feeling the cracking effort (CE) is still pretty high, either they just didn't do the service or they are employing a specialist who thinks like nickb that the CE is adjusted with the orifice (crown)........

    The A700 is a barrel poppet balanced 2nd with 'micro' adjustment screw, which means that in this case the orifice is almost exclusively used to adjust the lever height.

    The CE is then adjusted with the Adjustment Knob by the diver and the 'micro' adjustment screw by the technician.

    If you pressurize the reg and shaking the 2nd doesn't produce a rattling noise, probably the lever height is okay.

    If you don't want to go through the hassle sending back your reg to the dealer who seemed to do a poor job, you can do it yourself if you think that you are capable of that.

    If the lever height is okay (which I guess is), the adjustment procedure is pretty straight forward.

    You have to remove the decal on the Adjustment Knob carefully with something suitable like a small screw driver.

    Below you find a stainless steel screw with an o-ring which you can remove with 4mm Allen key.

    If the Adjustment Knob is screwed out as far as possible, you can use a 3mm flat screw driver, put it into the orifice down to the bottom and start to turn the micro adjustment screw counter clockwise until the A700 starts slightly to free flow.

    Now turn the screw clockwise until the free flow stops and then turn the screw about 30% further to make sure your adjustment will be stable.

    Check again the lever height by shacking the pressurized 2nd ( no rattle should to be heard) and you should have a nice breathing A700.

    Put back the metal screw and find some light glue to stick back the decal and you should be fine.

    BTW, it is not advisable to adjust the A700 extremely light to avoid light leakage from the exhaust valve underwater.

    Good luck!:)
     
    AdsDiving833 likes this.
  7. Wibble

    Wibble Fish don't talk
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    Dumb question... I've a couple of Scubapro Mk25s for Sidemount but I just don't get on with Scubapro second stages - don't like the fiddly switch. Have one G360 and a S555 (which is prone to freeflowing)

    Any reason why I can't swap these over for a couple of Apeks ATX40s? Different IP?
     
  8. taino

    taino New Member

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    Wibble, technically I don't see any problems switching the 2nds.

    The 2nds don't care where the IP is coming from as long it is within the specs.

    SP and Apeks use almost the same IP range for their 2nds.

    I wouldn't hesitate swapping the 2nds if I would see any benefit.......
     
  9. Scottish Diver

    Scottish Diver New Member

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    Thanks all for the comments and suggestions.

    I managed to get it sorted out at a local shop - turned out that not only was the cracking adjustment way off, the IP was out as well.

    Now to actually try it in the water!
     
  10. jb2cool

    jb2cool Moderator
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    ....ant to get your money back from the 'tuning'.

    How much did they charge to sort it?
     
  11. Scottish Diver

    Scottish Diver New Member

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    £20 which I think is completely reasonable considering that it needed tested and then adjusted on both the 1st and 2nd stages.

    The original company - £25 - by the sounds of things they could have only taken it further from the optimum tune than it would have been having come from the manufacturer and sitting for months!
     

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