Tuning Scubapro A 700 reg

[Ojai Diver]

So I have gotten into the bizarre regions of liability and self help.

My A 700 cracks, I am told, at about 1.1 inches of water. To me, this is only barely satisfactory for this rather expensive reg. Like a parent with a bright, underperforming child, I am convinced that it "can do better." The reg now almost never free flows, nor does it leak. Both to me suggest it is undertuned. I have spoken with two different technicians on this, and both seem reluctant to tune this reg hotter. Both seemed think I should be turning cartwheels of joy at it being at 1.1. Regarding further adjustment, the last tech finally told me, "I can't do it, but you can." He then gave me the rundown for adjusting the set screw.

On the set screw is plastic cover with the + and -. Is there any way to take this off without destroying it?

Any other cautions or tips for performing this job? My first stage is a Mark 11, so I am told there is a good amount of IP swing.

Thanks.

 

[tbone1004]

I'll disclaim that if you are thinking about adjusting it from the adjustment knob and asking about removing that, then I would urge you to not do this as it demonstrates a lack of understanding in how that regulator is assembled and functions.

If you're going to do it, you need a tank at whatever pressure gives your MK11 the highest IP. I don't know if that's low or high pressure since I'm not familiar with that first stage, but you'll need one of them.
From there, you put the adjustment knob as far to + as you can, and adjust the lever with an inline adjustment tool until it JUST barely starts to leak. That is as hot as you can get it without freeflow. It won't be much lower than 1.0" though. VERY few regulators can be tuned stable below 1.0" and most of them have a yellow whale on their logo...

 

[Ojai Diver]

I'll disclaim that if you are thinking about adjusting it from the adjustment knob and asking about removing that, then I would urge you to not do this as it demonstrates a lack of understanding in how that regulator is assembled and functions.

Not removing the adjustment knob, but adjusting it from that side. That is what the tech specifically told me--not the hose side-- so if it is my lack of understanding, it is also his.

I don't claim a lot of knowledge in this, hence my post.

 

[tbone1004]

Not removing the adjustment knob, but adjusting it from that side. That is what the tech specifically told me--not the hose side-- so if it is my lack of understanding, it is also his.

I don't claim a lot of knowledge in this, hence my post.

the adjustment knob is there to minimize the risk of it freeflowing. Usually if it's on your secondary or if you're going into high flow. It is supposed to be all the way on the + side when you are breathing on it. It is not part of the "tuning" procedure aside from making sure it is all the way to the + side and there are no adjustments that can be made by removing it.
The hose side is where you make actual adjustments to the cracking effort of a second stage.

This is how it's done. Was done on a Sherwood, but it is how most all second stages are adjusted.

 

[halocline]

The MK11 IP will be highest at low tank pressure.

The old-school SP regs have an extremely simple cracking pressure adjustment; simply remove the hose, and adjust the orifice with a screw driver. I'm not familiar with the A700, but I bet it's more complicated. I think I have a schematic, after lunch I'll look it up.

1.1" of water is nothing to write home about with regards to cracking pressure. However, you do have to consider case fault geometry. You can't generally adjust a 2nd stage to crack at less pressure than the dept differential between the diaphragm/lever connection point and the exhaust valve.

 

[shurite7]

Why do you think adjusting it to less than 1.1 will make a difference? SP specs state 1.0-1.4 on the A700. Up here in the cold high elevation lakes I adjust the A700 to 1.3-1.4. Adjusting to 1.0 is not going to make a huge difference to the second stage.

I've played around by tuning second stages to as low as .9 and found they breathed very easy, but become unstable in the water, especially colder water. The lack of stability isn't worth the presumable easier to breathe.

 

[Newdiv]

There is a microadjust behind the sticker. You have to remove the screw and knob as well. You can turn it counter clockwise to create a free flow then clockwise to just stop it. Check the inhalation effort. This will not move the lever. I find that the purge button can get very touchy if you try to go too low and a current can purge your reg.

 

[Ojai Diver]

the adjustment knob is there to minimize the risk of it freeflowing. Usually if it's on your secondary or if you're going into high flow. It is supposed to be all the way on the + side when you are breathing on it. It is not part of the "tuning" procedure aside from making sure it is all the way to the + side and there are no adjustments that can be made by removing it.
The hose side is where you make actual adjustments to the cracking effort of a second stage.

This is how it's done. Was done on a Sherwood, but it is how most all second stages are adjusted.

I understand what you are saying, and I have previously watched this video already. (I enjoy Alec Pearce's videos.)

However, the tech told me specifically that the tuning on this particular reg was done from the knob side (separate and apart from its adjustment function) NOT the hose side--unlike most seconds.

I have looked for a diagram or manual, to no avail. Until I get some clarification, I'm not touching it.

 

[Newdiv]

However, the tech told me specifically that the tuning on this particular reg was done from the knob side (separate and apart from its adjustment function) NOT the hose side--unlike most seconds.

It’s actually a combination of both sides

 

[tbone1004]

I understand what you are saying, and I have previously watched this video already. (I enjoy Alec Pearce's videos.)

However, the tech told me specifically that the tuning on this particular reg was done from the knob side (separate and apart from its adjustment function) NOT the hose side--unlike most seconds.

I have looked for a diagram or manual, to no avail. Until I get some clarification, I'm not touching it.

as @Newdiv said, there is the "macro" adjustment that is pretty standard and that's on the hose side. The micro is under the sticker, but to me if the IP is changing at all, you can only ever get so close.

If Scubapro says 1.0 is the min on spec, then it MIGHT be able to go to .9, but will be relatively unstable that low. If it's stable at 1.1 you won't really be able to tell a difference.