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View Full Version : SPG needle stuck at 50o



mksmith713
02-17-2009, 09:25
I have two older Scuba Pro SPG's and both have the needle bottoms out at 500 psi on both of them.
Is there anyway to reset them to zero?
I like these old brass and glass SPG's and would hate to just toss them.

I've already unhooked them from the 1st stage, tapped on the glass, etc.

awap
02-17-2009, 09:56
That front ring on the SP gauges will unscrew. I have removed the ring to replace the o-ring on a leaker and to repair the lense (it is plastic). I'm refering to the older 2" SP SPG but I'm sure the newer, larger (2.25") can also be disassembled.

If I were going to try to adjust the needle, I think I would try hooking it up to a tank, with the cover & lense removed, to put it under pressure and then try to adjust the needle the desired amount. Once corrected, use a little glue to hold it in place. But you will want to monitor it's accuracy for a while to see that it holds. The o-ring that I used to reseal the face was a 2-032. I would not suggest trying to reuse the old o-ring as it will have taken quite a set.

Edit: BTW, I'm assuming the problem is that the needle has become loose on the stem. If the needle does not move fairly easily and stay where you move it to, then it may be a problem with the me mechanisms driving the needle. If that is the case, I'd probably treat the SPG as dead and do the appropriate autopsy. I've never had the opportunity to venture behind the scale into the working parts before.

mksmith713
02-23-2009, 15:46
The face on my old SPG are glass and they aren't unscrewing for anything.

keyshunter
02-24-2009, 04:38
Spg's are too inexpensive to fool with and then gamble that they will read correctly at depth. I would save the hose and the spool and pitch the rest.

awap
02-24-2009, 06:00
Spg's are too inexpensive to fool with and then gamble that they will read correctly at depth. I would save the hose and the spool and pitch the rest.

"Too inexpensive" is an interesting concept. Their cost is similar to a car tire. When you get a flat, do you patch it or throw the tire away.

Some SPGs can not be disassembled so you have no choice but to retire them. One nice thing about a repairable SPG is the repair can be tested so you don't need to be any more concerned about its functioning at depth then you should be about a new SPG.

fire diver
02-24-2009, 06:39
Some SPGs aren't worth trying to save, but a brass and glass one I would at least try.

Without knowing the nature of what caused the failure, it's hard to give an opinion. I guess you really can't hurt it at this point.

mksmith713
02-24-2009, 07:22
They're both glass and brass and being the tinkerer I am, I'm gonna play with them.
I recently came upon an older plastic SPG from Dacor.
You couldn't even see what kind of guage it was because it was so abscured with dried salt.
The entire thing was white on the inside.
I took it apart, cleaned out all the salt and found where there was a small crack that allowed water in.
I repaired the crack with 2 part epoxy and put it all back together.
The O-ring was still in great condition, so I put a little silicone grease on it, got it hooked up on a tank I keep out in the garage and voila, it works like it's brand new.

I never throw anything away until I disect it first.
At the very least, I'll learn a little about the inner workings.

Gombessa
02-24-2009, 09:49
I would a little worried about using an SPG that is failing in any significant way. I know old-timers used to dive without an SPG, and it's ideally a 'backup' for what you should already know given your scr/time, but for $60-90 I'd just replace it. My worry is not that you'd see it at 500 and figure you can breathe it down to zero, but that it may be broken or later break in a different way, one that may not be as obvious.

No harm in an autopsy if you just want to tinker of couse.

calwolf
02-24-2009, 09:55
I never throw anything away until I dissect it first.
At the very least, I'll learn a little about the inner workings.

Fantastic approach to life...

When you've got something that just needs a little fixin', why waste precious resources on another?

"Use it up, wear it out, make it do, or do without!"

But uh... if it doesn't work, don't go without a pressure gauge ;)

mksmith713
02-24-2009, 11:16
Oh...I'd never go wothout a pressure guage.
But do you REALLY trust your guages 100%?
I don't.
That's why I carry a 13cf pony......
If my guage is off and I'm in an OOA situation, I'm covered with at least enough air for an ascent from NDL depths.
If I were to dive deeper, I'd carry an AL 80 as redundant.

Gombessa
02-24-2009, 11:47
Oh...I'd never go wothout a pressure guage.
But do you REALLY trust your guages 100%?
I don't.

I never trust my SPG 100%. But if I knew it was broken in that it stuck at 500psi, I'd wonder what else might be wrong with it, and at that point I wouldn't trust it even 1%, and thus I wouldn't dive it.

But I would tear it apart and check out the bourdon tube mechanism!

mksmith713
02-27-2009, 13:31
After opening it up and playing with it a bit,I decided to chuck it.
Thanks for all the responses.

awap
02-27-2009, 14:02
After opening it up and playing with it a bit,I decided to chuck it.
Thanks for all the responses.

If you have not hauled out the trash yet, I'll buy the lenses from those gauges. I have one with a cracked lense that I have repaired but I'm not sure it will last.