Subjective evaluation G250V vs. D400 vs A700 vs Bal Adj.

[elan]

So we had a chance to have all 4 in the water on the same dive.

D400 on MK20 (IP 130)
A700 on MK17 (IP 130)
G250V on MK17 (IP 130)
109 converted to Bal Adj (IP140) , (converted using the single o-ring poppet - not an s-wing poppet)

Checking all those regs around 30' gave us the following results of subjective performance
1. D400 - the easiest breather.
2. Bal. Adj.
3. A700 (was only slightly harder to breath and less smooth air delivery than Bal. Adj.)
4. G250V

All barrel 2nds were tested at the easiest setting at the edge of he case geometry fault when the cranking pressure was set tight enough to stop bubbles from the exhaust while looking down. D400 was set to .6 on the 2 cent magnahelic.
I kind of realize that Bal Adj had a higher IP first which contributed to a smoother breathing effort I believe.

Although the A700 looks like an expensive option, I still believe its a great option if you want a modern reg in metal case. Although the tech at the dive shop said I would pee my drysuit once I feel how easy it breathes I think my pee was all spent for D series and Ait 1 longtime ago
G250V is a great contender and and worth getting if one wants to be "cave compatible" and do not want to mess with regs doing the rebuilds.
If DIY is an option a Bal Adj and D series I believe are the best value for money. And a D-series is IMHO still the best breather from all the SP regs I have tried (not counting the AIR1 and the double hose regs).
It is amazing how a so old reg like a converted 109 holds it's value so well. To be fair to the A700 I would guess the 109 in it's time was priced not lover than A700 is priced today ? Maybe someone can tell us how much those regs were sold for back than.

 

[halocline]

Shhhhhh.......don't burst the the bubble. I only have 5 D300s left and 6 or so 109s. I might need more. OTOH, if enough people were fully aware of the performance benefit of the center balanced coaxial 2nd stage design, maybe SP would do something smart for a change and bring out a reissued D series reg.

I'm worried that the days of finding a SPEC equipped MK10/D300 in like new condition for $85 on ebay are over. Of course, awap might find that price to be a bit high for his tastes.

But then again, there's always the titanium atomics for those who must spend a fortune in order to 'breathe easy'.

 

[Zung]

I once did a similar experiment with a BA and a G250, the only differences were:

• Both 2nd's connected to the same 1st
• Both 2nd's tuned to .8"

Under those conditions, I had a slight preference for the G250, I think mostly because of the stronger Venturi of the G250 (set at mid range), kinda like the kick down in an automobile.

 

[elan]

Shhhhhh.......don't burst the the bubble. I only have 5 D300s left and 6 or so 109s. I might need more. OTOH, if enough people were fully aware of the performance benefit of the center balanced coaxial 2nd stage design, maybe SP would do something smart for a change and bring out a reissued D series reg.

I'm worried that the days of finding a SPEC equipped MK10/D300 in like new condition for $85 on ebay are over. Of course, awap might find that price to be a bit high for his tastes.

But then again, there's always the titanium atomics for those who must spend a fortune in order to 'breathe easy'.

May be HOG will try to create one ? I hope the patents if there are any might be close to the expiry date

I have recently acquired another D400

 

[agilis]

I have a new old stock D300, still in its box, never been in water. Any opinions on the kind of service will it need before it can be safely used? I assume that at least the o rings should be replaced, though what I can see looks pristine and the reg works perfectly on land, attached to a Mark 10. I've been doing my own maintenance on SP 109/156s, G250s, Mark 5s and Mark 10s for many years, but these are fairly simple to work on and very familiar to me. The D300 is a complete unknown, but I'm looking forward to using it. A Scubapro dealer tells me that they tend to flood when you are in an inverted position, but I'd prefer to see for myself.

 

[halocline]

If you leave it pressurized, maybe purge it lightly 50 times or so and it doesn't bubble, and it holds vacuum, it's very likely fine to dive. Rebuilding these regs is really quite easy, with one nasty exception. That's removing the pre-dive/dive switch, pulling the spring lever out, and reassembling that set up. Unfortunately, you need to do that in order to completely disassemble the regulator if you want to replace all the o-rings. The ones that typically get dried up and useless are the 021 (maybe 022?) cap o-ring, which on yours is likely red, and the pre-dive switch o-ring, which on yours is likely a square molded o-ring but maybe not. The early originals were round, you just had to work them into the square channel. It's a pain, but it works fine.

Just take a few photos, note especially the orientation of the spring and the regulator lever, consult a schematic (they're floating around) and you shouldn't have any problem. Bryan at vintagedoublehose.com has kits for sale (I know because I put them together) that include all the o-rings on the reg as well as a new poppet. You'll need to re-use your adjusting screw for the lever, but I've never had one loosen up. You could coat it with a drop of nail polish if you were worried.

The predecessor of the D series, the air1, did tend to breathe a little wet inverted, at least the 4 or 5 of them I've tried all have. One 'improvement' on the design with the D series was the coaxial exhaust valve mounted on a plastic rim on the diaphragm, rather than just using the diaphragm itself as an exhaust valve on the pilot and air1. I have found that with a good exhaust valve and diaphragm, the D300 breathes about as dry upside down as a typical barrel poppet 2nd stage.

 

[agilis]

Thank you, Halocline. You have an enviable ability to be both detailed and concise. My copy of Vance Harlow's book recommends avoiding D series, but they are fascinating. A small winter project.

 

[Nemrod]

Since the work of breathing includes both inhalation and exhalation, I think that is were the 109 falls a little short. It has only a 25mm exhaust valve, isn't it? Subjectively, using a 109 against a Titan XL or Legend XL, the modern AL products win, but again, that is subjective and my one use of an A700 left me wanting one badly but, I would not trade my 109s for a new one, I love them way to much. The tiny bit of difference in total breathing effort, if any (I admit, mine is an opinion), is negligible and of no real consequence for any sport diver.

N

 

[elan]

I think I used 022 for the cap on the last rebuild ...

One thing to remember is to give anough play in the lever while adjusting the cranking effort and also turn the effort screw past that point back and force few times so the spring sets itself properly. I found that lubricating the ends of the spring helps. After the effort is set adjust the lever play. Halocline skipped that point as him and DA Aquamaster posted it here may be at least 20 times just search D400 on the forum and you will find a wealth of info on how to rebuild these babies. DAAM also recommended to put new popets into a ultrasonic cleaner for 5 mins and that did help me a lot to get consistent tuning.

---------- Post added November 25th, 2012 at 07:12 PM ----------

Since the work of breathing includes both inhalation and exhalation, I think that is were the 109 falls a little short. It has only a 25mm exhaust valve, isn't it? Subjectively, using a 109 against a Titan XL or Legend XL, the modern AL products win, but again, that is subjective and my one use of an A700 left me wanting one badly but, I would not trade my 109s for a new one, I love them way to much. The tiny bit of difference in total breathing effort, if any (I admit, mine is an opinion), is negligible and of no real consequence for any sport diver.

N

Nemrod you are correct about sizes, the. Exhaust on the A700 is noticibly bigger.
I would not trade in an 109 for a A700.
I just got a great trade in deal on a slightly used set of mk17/A700 and I traded in an mk10 with a crappy mares second. But I would not pay 500+ for a new A700 as SP wants, no way. But I do like the reg. Especially in our supercold waters a brass reg helps.

 

[Nemrod]

I think I used 022 for the cap on the last rebuild ...

One thing to remember is to give anough play in the lever while adjusting the cranking effort and also turn the effort screw past that point back and force few times so the spring sets itself properly. I found that lubricating the ends of the spring helps. After the effort is set adjust the lever play. Halocline skipped that point as him and DA Aquamaster posted it here may be at least 20 times just search D400 on the forum and you will find a wealth of info on how to rebuild these babies. DAAM also recommended to put new popets into a ultrasonic cleaner for 5 mins and that did help me a lot to get consistent tuning.

---------- Post added November 25th, 2012 at 07:12 PM ----------



Nemrod you are correct about sizes, the. Exhaust on the A700 is noticibly bigger.
I would not trade in an 109 for a A700.
I just got a great trade in deal on a slightly used set of mk17/A700 and I traded in an mk10 with a crappy mares second. But I would not pay 500+ for a new A700 as SP wants, no way. But I do like the reg. Especially in our supercold waters a brass reg helps.

True, true, true, but (always a but) I think, corrected for inflation, the 109 with Mark V was at least as expensive, or close, in 1976 as the A700 is today. In fact, since I was a poor college student, I could not afford a 109 then anymore than if I were a poor college student today could afford an A700 rig. But, I graduated with a M.S. and owe no money so maybe kids now could buy one with left over college loan money or something, dunno.

Using an inflation calculator, 200.00 1976 dollars would be 813.07 2012 dollars.

Thanks for the evaluation, you have managed to cool my desire for an A700, my wife thanks you.

N