Scubapro 156 and 108 first stage advice.

[Tr4lover]

It is very possible. I am having to replace the case ring screws I will definitely take a look again. I remember the covers where built different.

So should be like this?

 

[p_kos]

So should be like this?

Correct.

 

[Tr4lover]

Correct.

Thanks everyone!

 

[Couv]

Credit to @DA Aquamaster for the 108 attachment.

 

[axxel57]

It's sure a 156 with CE stamp, not a 150-151 or 154?

 

[Open Ocean Diver]

It's sure a 156 with CE stamp, not a 150-151 or 154?

Do you know when the 156 with CE stamp first came out?

 

[axxel57]

Do you know when the 156 with CE stamp first came out?

That was in 1997 for their last BA Model.
Your beauty is the very last model.

 

[johndiver999]

This unit has a fixed orifice unfortunately. Thanks for the knowledge. The case also uses the dual exhaust diaphragms. But I've been told a single works just fine. Breathing is much harder with both diaphragms installed.

not sure if the guide mentions this - probably, but if the second stage does not hold a tight vacuum (i.e., it leaks water when diving) then you need to remove the exhaust piece and then polish and clean any corrosion you find under the lips of the exhaust valve(s). Any roughness will cause a quite annoying leaky, wet breathing regulator. I often have decent luck with steel wool. but some vinegar and a nylon scrub pad might work if it is not too bad. It is a common problem from what I seen on old metal second stages.

 

[John C. Ratliff]

Very nice! Only thought is once you service the MK17 tune the 108 at low tank pressure (300-500 psi) when the IP is highest since it’s an unbalanced second stage. The MK17 is “balanced” but the IP can still be around 10 psi higher at low pressure.

Okay, I’m rather confused. My understanding of the physics of regulators is that the IP is set by the first stage, and that on a balanced first stage, it doesn’t matter what the tank pressure is. But with an unbalanced first stage, you need to set it at a high pressure if it’s a piston regulator (IP will be highest at high pressure—the opposite of a diaphragm first stage).

Now, the second stage being “balanced” means only that the inhalation lever sees the same pressure throughout the breathing cycle, as the variation of pressures from the line due to the breathing cycle will not affect the lever. This may be false, as my understanding came before there were balanced second stages. But I don’t think there is a reasonable explanation as to why the second stage would influence the IP.

SeaRat

 

[p_kos]

Okay, I’m rather confused. My understanding of the physics of regulators is that the IP is set by the first stage, and that on a balanced first stage, it doesn’t matter what the tank pressure is. But with an unbalanced first stage, you need to set it at a high pressure if it’s a piston regulator (IP will be highest at high pressure—the opposite of a diaphragm first stage).

Now, the second stage being “balanced” means only that the inhalation lever sees the same pressure throughout the breathing cycle, as the variation of pressures from the line due to the breathing cycle will not affect the lever. This may be false, as my understanding came before there were balanced second stages. But I don’t think there is a reasonable explanation as to why the second stage would influence the IP.

SeaRat

Second stage does not influence IP but an unbalanced second IS influenced by IP. When you set the cracking pressure on an unbalanced second you need to do so at a tank pressure where it will see the highest IP (high tank pressure for a piston and low pressure for a diaphragm). If you set your unbalanced second at high pressure, then when the tank pressure drops to 300-500 psi and IP rises on a diaphragm first (even on a balanced first it can go up as much as 10-12 psi) it may cause the second to free-flow (if your second was tuned at the edge of easy breathing). Hope that explains it.