ScubaPro G250 Graphite - How old?

[halocline]

It needs a new seat as there is a small air leak (one bubble every 3-4 seconds).

Just a guess, but I wouldn't be surprised if that slow a leak was due to a worn balance chamber o-ring/ balance chamber or some IP creep. To check, you'll need an IP gauge; just connect the reg and watch the gauge. If it slowly creeps up until a bubble emerges, then drops back down and starts over, you have a 1st stage problem. If it's a MK10, probably the piston edge is a little nicked or there's wear in the seat.

If the IP doesn't creep up, I'd suspect the leaky balance chamber. That single tiny o-ring and the plastic balance chamber might not be making an air-tight seal. The newer poppets have a back-up o-ring.

 

[Couv]

Concur with Halo on this one. You need an IP gauge. Worn/bad o-rings on the poppet stem are usually indicated by a steady stream of pea sized bubbles. A bad low pressure seat is usually indicated by a hiss, slight to heavy depending on how bad it is. A release of gas that stops after purge and then begins again points to a first stage issue. ALWAYS verify the IP before attempting to troubleshoot or repair the second stage.

 

[raftingtigger]

IP is fine. 135 and rock solid. Not only that but it has the same very slow leak when attached to a different 1st. Another old 1st does have an IP creep, but the symptoms are very different. In that case if you let the 2nd sit it will start free-flowing. As soon as you either breathe or purge the free flow stops. Needless to say that one is currently off-line.

Might be the single o-ring on the poppet stem. I've all ready lubricated it, but will replace it before trying to replace the seat.

 

[raftingtigger]

Update on my G250g leak. After putting the (connected to IP) air barrel in water the leak appears to be from the upstream end of the air barrel. That suggests it is from the crown/cone/orifice o-ring or LP seat on the poppet. You can see by my terminology I've now read significant parts of Vance Harlow's book.

Dismantling it entirely, the poppet is grey with a metal stem and a single o-ring. The LP seat is riveted in. I was unable to extract the orifice to replace the o-ring. It unscrews just fine, but stops advancing with about 5mm to go. Per the SP manual I tried using a wooden chopstick, but without using a lot of force it wouldn't budge.

Not wanting to do damage, I took it to the LDS for service. They automatically return parts.

One question: reinstalling the poppet and lever is tricky. Sometimes it would go in right and others not. Also when I was depressing the lever (to adjust the orifice) it started only returning 1/2 way. This left the regulator responding to an inhalation effort fine, but the purge button wouldn't reach. Any tricks for the future?

I did just service my Conshelf XIV 1st w/o problems. Bad IP creep to start. Once done it has a rock solid IP of 140. Now on to my original (1971) SP MK 7. Not only am I learning a lot, this is FUN!

 

[Zung]

No tricks, only the triangular parts of the poppet must point to the aspirator/mouth piece and aligned with the axis formed by the 2 "feet" of the lever. Lift the lever, insert the poppet at the right angle, the spring and the balance chamber, a little push with a pencil and you should feel it clicks in.

Easiest way to do it is with the barrel outside of the case so you can see through the holes for the feet of the lever. Fit the adjustement knob and check the mouvement of the lever: it should be smooth through its travel and bounce right back if you let go (don't do that too many times). Press the lever all the way down to fit the whole assembly into the case.

You can see how the lever engages the poppet here: