ScubaPro D400 2nd stage freeflow problem

[redacted]

Okay, so here's an update on the D400 2nd stage. I contacted my LDS and told them that I may be able to get the parts needed to fix my reg if their tech can tell me what it needs. The tech told me that he wouldn't use a D400, thought it looked funny, that it wasn't very popular which is why they didn't make them for very long. That isn't what I'm hearing here on SB. Another local shop is a Scuba Pro dealer. I guess I'll give them a try.

Steve.

The D-series is different fro m other Scubapro regs and it sounds like the tech does not know how to service it and is unwilling or unable to learn. Find another tech.

 

[halocline]

The D series (D300/350/400) was among the best performing 2nd stages ever made. It's a little different to work on from conventional 2nd stages, but any SP tech worth anything should be familiar with them. The guy that had yours doesn't know what he's talking about.

 

[scubafanatic]

.......sounds like you have a decision to make.....either be prepared to ship you reg off to someone who knows that they are doing (DA Aquamaster) everytime you need it serviced/adjusted....or take DA Aquamaster up on his offer to do the 2nd-stage 'swap' , that way you can have your reg serviced locally ...... although honestly, based on what I've heard, if this guy is so clueless about the D400, I'm questiong his expertise/skills across-the-board.

 

[DA Aquamaster]

Okay, so here's an update on the D400 2nd stage. I contacted my LDS and told them that I may be able to get the parts needed to fix my reg if their tech can tell me what it needs. The tech told me that he wouldn't use a D400, thought it looked funny, that it wasn't very popular which is why they didn't make them for very long. That isn't what I'm hearing here on SB. Another local shop is a Scuba Pro dealer. I guess I'll give them a try.

The D300/D350/D400 were basically the same design with some minor evolutionary changes. The design itself was a development of the Air 1, which was a major redesign of the Pilot substituting the pilot valve for an easier to adjust center balanced valve design.

The major difference between the Air 1 and the D series was they moved the diaphragm around to the front of the reg. So the valve design itself was around since about 1977 and the D300 came long about 1979 with the D350 and D350 each coming out a couple years after the other. The D400 itself was in production from the mid 1980's through 2004 when it was finally discontinued.

So, even if you discount the 10 years of Pilot, Air 1, D300, D350 evolution and look at only the D400 production, it was in production for 20 years, and was billed as Scubapro's premier (and most expensive) second stage for 15 of those 20 years. It's hard to say it was not around long, but it is very accurate to say it was not around long enough if you have ever used one that is properly tuned.

Scubapro discontinued the D400 in large part because the valve design is different and requires much different adjustment techniques. Scubapro intended to replace the D400 with the X650 to increase the standarization of parts and service techniques as the X650 used a shorter version of the same poppet and the same seat used in all the other SP balanced second stages. Unfortunately, the engineers on the X650 project apparently missed the point of the angled diaphragm and co-axial exhaust valve, or failed to realize the significance of it in the water, or perhpas just could not figure out how to make the lever work with a coaxial exhaust valve/diaphragm. In any event, without it, the X650 performed no better than the S600 and never offerred the same advantages in case geometry fault as the D400 (The D400 basically breathes super easy in any orientation).

So in short, the D400 was discontinued because it was harder to service and required each new tech to be trained to service it specifically rather than just a generic course covering normal single and dual adjustment designs.

A contributing factor was also that the D400 sufferred significantly from CE certification and other "improvements" during it's long production run. the worst fo these was the switch to a separate aspirator and plastic orifice. The new (post 1994) orifice does not offer the same sharpness or fine degree of performance and SP made some changes to the lever that I think made it more freeflow resistance in terms of meeting the incredibly stupid and useless CE freeflow requirement, but appears to have increased the inhalation effort needed to sustain flow during inhalation. So by the time SP dscontinued it, they could legitamately argue that it did not offer much advantage over an S600 due to all the detuning it had sufferred over the last decade of its production.

When it got long in the tooth from a marketing perspective, it was not promoted heavily by Scubapro, so it is perhaps also accurate, but misleading, to say it was not very "popular" in 2004 when it was discontinued.

But it remains perhaps the best second stage ever mass produced and its major competition in that regard is the G250 introduced around the same time period. Sp recently brought the G250 back as the G250V and it would be great if they revived the D400 in its original metal orificed form as well.

 

[scubafanatic]

...if you've just gotta have one of there regs...there is a nice one up for sale on E-Bay right now: item # 200377767850

 

[m_tsurayaba]

T

A contributing factor was also that the D400 sufferred significantly from CE certification and other "improvements" during it's long production run. the worst fo these was the switch to a separate aspirator and plastic orifice. The new (post 1994) orifice does not offer the same sharpness or fine degree of performance and SP made some changes to the lever that I think made it more freeflow resistance in terms of meeting the incredibly stupid and useless CE freeflow requirement, but appears to have increased the inhalation effort needed to sustain flow during inhalation. So by the time SP dscontinued it, they could legitamately argue that it did not offer much advantage over an S600 due to all the detuning it had sufferred over the last decade of its production.

Seems like a good 2nd stage to get if one can find it.
Which period D400 would be the best ? You mentioned pre 1994 (thats 15 years ago!!)
Is there a serial no denoting year of manufacture ?

 

[DA Aquamaster]

Pre-1994 is a safer bet. There is no doubt a serial number denoting the transition, but I don't know what the cut off would be.

The D350s and the early D400s have a rubber purge cover with lines molded in it running across the cover, as opposed to later D400s that have a series of rounded rectangles molded in the cover. It does correlate exactly with any other change, but is a broad indicator of an early versus late D400. The latest D400s are also marked to indicate they meet CE standards and for a D400 that is generally a bad thing.

But none of the above may mean much. Some older D400s may have ended up with newer aspirators and plastic orifices if the original was damaged and some may have been "upgraded" with newer levers. Replacement purge covers are rarely encountered as they don't seem to wear out, but finding a D350 with a replacement D400 decal is very common and probbaly not intended to miselad anyone as the D350 decals were not available as long as the replacement D400 decals.

On the other hand, I have had some newer D400s that breathe exceptionally well when all the parts seem to be working in perfect harmony, it is just not as common in them while it is an easily achieveable norm in the older D400s.

 

[ScubaSteve2000]

Mine seems to be an older D400. At least it has the rubber purge cover with the lines. I don't see a serial number. It has a blue "switch" with an arrow and the word "Dive". I'll find out this weekend if it can be fixed.

 

[redacted]

Mine seems to be an older D400. At least it has the rubber purge cover with the lines. I don't see a serial number. It has a blue "switch" with an arrow and the word "Dive". I'll find out this weekend if it can be fixed.

The blue switch is the mark of a D300. The D400 and D350 have a black switch with a decal marked "D350" or "D400". I just put a D300 back into service today. A good cleaning and a new poppet left it with a cracking pressure under .75 inches of water. I actually detuned it to closer to 1.0 inches. They are smooth, easy breathers.

 

[DA Aquamaster]

As awap indicates a blue switch is the hallmark of the D300. The D350 was very similar and early D350s used the same D300 case, while later D350s used a newer case that was also used on the D400. The basic difference is that the lever is a bit longer on the D350 compared to the D300, and the D400 uses a slightly different lever that faces the other direction.

A good D300, D350 and D400 will all provide the same excellent inhalation performance and if you were blind folded, you'd never be able to tell the difference. They were in effect the same design with just minor detail improvements over time.