ScubaPro G-500

[Rusty Shackleford]

I picked one up in with an Ebay purchase where I really wanted the rest of the stuff.

It appears to be in excellent shape.

I have no desire to upgrade it to a 600. Mine has the chromed brass air barrel(yay!). It appears to be clean and very lightly used. What rebuild kit do I use, the one for the 600?

I also noticed this recall notice:

CPSC, Scubapro Announce Recall of G500 Second Stage Regulators Used in Scuba Diving

How can I tell if the work was done? Was it a replacement of the VIVA vane or of the housing? Or was it bad O-Rings? What was the nature of this fault and what was the corrective measure?

 

[Rusty Shackleford]

Ok, mine is an Italian, apparently made in 98 if I read the serial numbers correctly. But it has a metal air barrel. Go figure. So it was NOT subject to the recall. I also found an G-250HP/G-500 service kit in my old stock.

It has the early S-wing poppet and it had a white plastic washer that slips over the poppet to cushion where the spring terminates against it. It is also a single o-ring poppet.

It is getting replaced with a newer S-Wing poppet.

 

[Rusty Shackleford]

Except for the final tune, it's done. I have to get my test bottle out of storage.

No surprises, the metal was clean and everything went back together as it should. I have the never before used balance chamber tool cranked inside of the knob ready for use. I cleaned the R-390 that I am going to pair with it, flipped the puck and re-assembled (It looked so good, little was necessary, I didn't feel a re-build was necessary as clean as it was.)

It now has an up to date poppet assembly.

 

[Rusty Shackleford]

Help! I can't get the damn thing to stop free-flowing until it is like 2.0 on the cracking effort.

This thing is starting to get my goat!

I am using the Orafice to adjust the lever height and the balanced chamber to quench the free-flow. Obviously, if the lever is contacting the diaphragm, it will cause a free-flow in it's own right.

 

[Rusty Shackleford]

Ok, this one was a problem-child from the get-go.

It would not hold tune and leaked no matter what I did unless I had it tuned to like a two cracking pressure.

I ended up replacing the orifice and the LP top-hat seat. No change. Then I replaced the poppet and spring.

Fixed it.

I am leaning towards blaming the two tiny O-rings on the poppet or the S-wing poppet itself.

The ones that give you the most grief also teach you the most I have observed.

I have also learned how much I hate that pointless balance chamber.

 

[Rusty Shackleford]

And the book says cracking pressure could be as light as a 0.9. I don't see how to get there.

Someone remarked the euro version is de-tuned. How did they de-tune them? Lever length?

 

[rsingler]

Lots of commentary to work with here. I apologize in advance if I suggest things you already tried, or theory you are already familiar with.

Since you solved the problem with a new poppet (and spring), let me ask if you checked the poppet/balance chamber seal before you installed? With the poppet built with its seat and o-rings, I seal the hole in the seat with my finger, and try to bounce the balance chamber to ensure that it seals well around the tiny o-ring. Did you have generous lube on the walls of the balance chamber? If the bounce test works, then I install the spring and rebuild the valve in the barrel.
As for the spring and your cracking effort, keep in mind that that "washer" pre-adds spring compression, and thus, pressure on the seat once it's sealed against the orifice. To get less spring tension, make sure balance chamber adjustment is screwed out as far as possible, and if cracking is still too high, remove the spring washer and reassemble valve without it.
Finally, if you were able to seal the valve seat to the orifice BEFORE you put the diaphragm on, then you should be able to get any cracking effort you want, unless the lever is way too high, as might happen if the feet of the lever were bent by a previous tech to the wrong angle.
Keep in mind that before we had balance chamber adjustment (G250), we bent the lever to the right height after setting cracking effort solely with orifice pressure on the seat. Only with the addition of balance chamber adjustment did we use orifice to adjust lever height and spring tension to adjust cracking effort.
So if lever was too high for some reason, it's not surprising that you had to add too much pressure on the seat with the orifice, to drop the lever so the diaphragm wouldn't trigger it in the neutral position.

I'm unsure of where you are now. Reassembled, but unhappy with cracking effort is what I concluded.
I'd take diaphragm off, adjust orifice 1/12 of a turn past seal at your current IP, and see if diaphragm fits back on case without the diaphragm opening the valve as you screw the cover on. If not, let's talk about lever height.

 

[Rusty Shackleford]

"let me ask if you checked the poppet/balance chamber seal before you installed? With the poppet built with its seat and o-rings, I seal the hole in the seat with my finger, and try to bounce the balance chamber to ensure that it seals well around the tiny o-ring."

That is a good tip.

Playing with the balance chamber, I guessed it was a way to adjust cracking pressure independent of the lever height and that was it's true purpose.

Where should I set the adjust on the Balance Chamber at the start? All in or all out?

 

[rsingler]

Where should I set the adjust on the Balance Chamber at the start? All in or all out?

All out. Then just seal the orifice. Then add one hour on the clock face (1/12 turn).
Then see if diaphragm sits in its groove in the case without being lifted by the lever with pressure on the system.
If so, then screw on the faceplate lightly and start checking cracking effort. It should be below 1". If not, remove the components and take off the white washer that pads the spring. Reassemble and try again. Once you have a low cracking effort, use that special tool to screw in the balance chamber adjustment until it's where you want it (1.1-1.4"). Depressurize and remove the tool, and add the knob. Check to see if it's where you set it. If not, remove knob and screw adjustment in or out 1/8-1/4 turn until replacing the knob gives you what you thought you were setting with the tool. You're done! Knob all the way out is minimum (standard) diving cracking effort. Knob in adds cracking effort for "pre-dive" or surf entry or scooter riding, etc.

HOWEVER, if dropping the diaphragm lightly into place leaves the diaphragm dangling from the tip of the lever with the reg pressurized, then the lever is too high. You have two choices: drop the lever with the orifice (which will increase your minimum cracking effort - perhaps unacceptably), or drop the lever by bending the lever feet. If that's what you need to do, PM me.

Rob

 

[Rusty Shackleford]

Thanks Rob! This is the info I was looking for.