A change of heart, Scubapro D420

[James79]

I am rapidly moving toward this really being the best 2nd they make, at least in my opinion, I’m still playing with the James79 tuner, this thing can be adjusted down to near 0 cracking effort, wish the exhaust T were 3/8” longer but 95% of the time I don’t notice the bubbles at all.

I still owe you a replacement tuner... And starting tomorrow I've got a lot of time on my hands. So I can start modelling a wider exhaust T, if you send me some pictures of just the T with critical measurements. I figure I can work on the design, share pics of it on screen, and try a print when you think it looks right.
Respectfully
James

 

[lexvil]

I still owe you a replacement tuner... And starting tomorrow I've got a lot of time on my hands. So I can start modelling a wider exhaust T, if you send me some pictures of just the T with critical measurements. I figure I can work on the design, share pics of it on screen, and try a print when you think it looks right.
Respectfully
James

James, you don’t “owe” me anything until you let me pay you! It will be a few days before I can get to it, diving tomorrow and out of town Monday and it may be better to just send the reg and we can just work it from the other direction where the designer has the actual part in hand.

 

[James79]

Well, my design failed you, so I owe a replacement (just let me be stubborn on that point)! No rush on pictures/measurements, and I would rather you not send it here until I'm close to a prototype (I'll be doing at least one proof of concept to make sure my printer is up to the task).
Enjoy the diving!
James

 

[rsingler]

Credo che stiano ancora testando bene il prodotto, che qualcosa non è andato bene per ora, o addirittura vogliono aumentare le prestazioni, perché per ora sembra che MK19 abbia le stesse prestazioni dell'MK17 con la testa rotante in aggiunta.

I wondered what was keeping my order pending for so long. I've been waiting for a pair of Mk19/D420's for months, ever since my LDS first heard back from Scubapro. I've even already paid for them, to help out my LDS during the 'Rona! It's been a long wait.

 

[scrane]

So, is the d420 a viable option for those looking for a high performance regulator or only for those with the knowledge, the resources, and time to tinker with it? Is it a flawed concept or ahead of its time?

 

[rsingler]

So, is the d420 a viable option for those looking for a high performance regulator or only for those with the knowledge, the resources, and time to tinker with it? Is it a flawed concept or ahead of its time?

That's a really fair question @scrane ! Certainly, the ScubaBoard D420 discussions these past few months don't do much to raise your confidence, do they, lol!

My short answer is, "Definitely, yes! It's a high performance regulator!" And if not ahead of its time, it's at least bringing back the best of old technology. Think "Scubapro Pilot." But maybe wait a few months, for a couple of reasons. I don't know yet whether the tuning issues that have been discussed here are just as a result of DIY guys messing with our regulators, and causing our own problems, or whether there has been some inconsistency in factory assembly. My reg arrived just fine, albeit with a cracking effort that I thought was too high until I discovered more about the physics of this toy. But we've maybe had one other guy's reg arrive in a suboptimal tuning state. I have a couple more coming as soon as the Mk19 is released, so I'll have two more data points to add to the "factory new" tuning pool.

But I think there's also a second reason to wait a few months on this reg. Apart from whether or not it takes off from a sales standpoint, there aren't very many technicians who are intimately familiar with a center-balanced poppet design. The number of competent D-series reg technicians has dwindled over the last decade. That potentially means that, given the brevity of the Service Manual, if you bring your new toy in to the LDS for tweaking, it won't be intuitive to the technician what needs to be done. Our whole discussion about the contribution of diaphragm tension, and how long it took me to figure it out is testament to that.

But once the reg has been in the supply chain for awhile, and shops see it and service it, I think it could be a star! Certainly its performance outshines every other Scubapro regulator I own. Its breathing characteristics, both inhalation and exhalation, are so smooth! And from a service standpoint, it is faster and easier to service than literally everything.

Then again, it could all end up revolving around marketing. I mean, my Samsung is the best phone in the world! But Apple, for some reason, is eating its lunch.

In the interest of completeness, there's one final factor I'm waiting for more dive experience with this reg to assess. A barrel poppet design (G250, A700, S620Ti, Apeks ATX, XTX, MTX) has a knob you can crank down to raise cracking effort on your octo to prevent freeflow in the surf, or when you jump off a boat. Most also have a Pre-dive knob that changes Venturi effects, that also helps in this regard. The D-series had a slide switch and a spring that raised cracking effort in the Pre-dive position.
Well, the D‐420 has a novel Pre-dive switch design that both deflects flow and raises cracking effort about 0.1". I just don't know yet whether it's the simple but elegant engineering solution to an impact freeflow problem, or whether jumping off a boat may still cause issues. Certainly, when I had my freeflows in Key Largo, it was my own fault for tuning the reg too light. And it seemed to be better after I re-tuned it. But I don't have enough experience yet. I'll know more when my sidemount sets arrive, and I'm switching back and forth between regs repeatedly.
To give the superb Scubapro engineers their due, I'm sure they've addressed it. And as a primary regulator, it's a slam dunk. But can you use a matching D-420 as your octo? I want to, because when I primary donate (OMG, COVID!!!), I want my octo to perform just as well as my primary. I just don't know personally, yet, whether it will be trouble free dangling off my necklace, or in PADI's golden triangle.

Stay tuned...

 

[lexvil]

I agree fully with Rob, it just may be the real go to HP reg of the near future, but only having one sample that came horribly tuned it may be a better idea to wait a little bit for the training and experience to catch up to the design. I plant to acquire another once there are more out there (price lower) I do like it.

The hardest thing is letting go of so much of what you’ve learned, in the shop you can’t tune it to the edge like a conventional design, you can only get “ok” dry performance but once in the water it’s is a great breather, you can tell when it’s in “pre dive” unlike a g260 but it’s not like you can’t easily dive it that way, I’ve done it by starting with it in pre and once on the bottom thinking “oops” the funny thing is it preformed well until I switched it and it went to amazing.

It has become my “go to” regulator, it’s been holding tune fine which is important with no adjuster and hopefully with this design long term consistency will be a hallmark.

 

[buddhasummer]

Crow eating time.

Well, my D420 has traveled all over the world and is now back in my hands, thanks to both Lex and Rob.

It had a slight leak on arrival which was easily fixed by screwing in the top hex a bit. Tuned it to crack between 1.2-1.3". Seemed stable. Checked lever height, made sure it was just a hair below rim of case, pressurized I'd say there was about 1/2-3/4mm play between diaphragm and lever.

Initially I couldn't get it to free flow with Venturi open which initially made me wonder if my lever was too low, but after a quick chat with Rob and him using the word "brisk" tap I got it to free flow. Seems it's the same in that respect as an Apeks second stage and not like the frightening violent free flow you can get from a G250 just by pressing purge with Venturi on max.

Left it a few hours, air off, re pressurized it, checked cracking again and it had gone up a little. After a few breathing cycles it dropped mostly back to where I had previously set it. I think this is due to the "memory Foam" seat material, as previously mentioned by Rob, denting (?) the soft seat from spring pressure.

Good to go.

I took it out for a dive on Sunday, a ripping current, I was breathing very very heavy at @25m. The D didn't flinch at all and gave all the air I needed. I was impressed.

A slight change in head position greatly reduced the bubble interference I previously moaned about. I can live with it but am still hopping @James79 can make a wider one.

I installed the adjuster @James79 made and very kindly sent me, although I didn't need to use, I do like the look and it's nice to know I can if needed. Thank you James.

Post dive put the D on a gauge again and it was still at the 1.2-1.3" I'd set it at, cool.

The manual is wrong. If you tune as per manual you're likely to run into stability issues. As Rob has already identified lever height is critical, you must have a tiny bit of play. Set hex and check lever height again. Rob nailed it, again.

The way it breathes, the ease of disassembly and reassembly, the ease of tuning, now we know how, make this reg in my eating crow opinion a very very nice reg. Think it will be my favourite assuming it holds up over more diving. I'm going to dive it exclusively the rest of this year.

As everyone knows I like matching so hope Robs experiments using one as an octo are successful.

I like the no muss no fuss of the reg, I like that the Venturi is easily operated wearing dry gloves unlike the tiny silly "it's gotta be a joke" one found on some G250s. I like it's compactness and weight but of course most of all I like it's performance.

All previous complaints save it unstable on arrival are retracted. Assuming it holds up over time I think this could well be in balance the best second stage currently put out by SP.

To SP my humble apologies for doubting your engineers but you really do need to replace your manual writer.

To @lexvil a big thank you for taking the problem child off my hands when I was in financial sh.t and then letting me buy it back without pressure of re payment.

To @rsingler for taking the time to figure out the tricks and tips to tune it.

To @James79 for making the adjuster and having a go at a wider exhaust, I'll buy one off you for sure.

Stomachache commencing, crow tastes bad.

Thank you to all who helped. It's a great reg.

Take care
Simon

 

[lexvil]

Crow eating time.

Well, my D420 has traveled all over the world and is now back in my hands, thanks to both Lex and Rob.

It had a slight leak on arrival which was easily fixed by screwing in the top hex a bit. Tuned it to crack between 1.2-1.3". Seemed stable. Checked lever height, made sure it was just a hair below rim of case, pressurized I'd say they was about 1/2-3/4mm play between diaphragm and lever.

Initially I couldn't get it to free flow with Venturi open which initially made me wonder if my lever was too low, but after a quick chat with Rob and him using the word "brisk" tap I got it to free flow. Seems it's the same in that respect as an Apeks second stage and not like the frightening violent free flow you can get from a G250 just by pressing purge with Venturi on max.

Left it a few hours, air off, re pressurized it, checked cracking again and it had gone up a little. After a few breathing cycles it dropped mostly back to where I had previously set it. I think this is due to the "memory Foam" seat material, as previously mentioned by Rob, denting (?) the soft seat from spring pressure.

Good to go.

I took it out for a dive on Sunday, a ripping current, I was breathing very very heavy at @25m. The D didn't flinch at all and gave all the air I needed. I was impressed.

A slight change in head position greatly reduced the bubble interference I previously moaned about. I can live with it but am still hopping @James79 can make a wider one.

I installed the adjuster @James79 made and very kindly sent me, although I didn't need to use, I do like the look and it's nice to know I can if needed. Thank you James.

Post dive put the D on a gauge again and it was still at the 1.2-1.3" I'd set it at, cool.

The manual is wrong. If you tune as per manual you're likely to run into stability issues. As Rob has already identified lever height is critical, you must have a tiny bit of play. Set hex and check lever height again. Rob nailed it, again.

The way it breathes, the ease of disassembly and reassembly, the ease of tuning, now we know how, make this reg in my eating crow opinion a very very nice reg. Think it will be my favourite assuming it holds up over more diving. I'm going to dive it exclusively the rest of this year.

As everyone knows I like matching so hope Robs experiments using one as an octo are successful.

I like the no muss no fuss of the reg, I like that the Venturi is easily operated wearing dry gloves unlike the tiny silly "it's gotta be a joke" one found on some G250s. I like it's compactness and weight but of course most of all I like it's performance.

All previous complaints save it unstable on arrival are retracted. Assuming it holds up over time I think this could well be in balance the best second stage currently put out by SP.

To SP my humble apologies for doubting your engineers but you really do need to replace your manual writer.

To @lexvil a big thank you for taking the problem child off my hands when I was in financial sh.t and then letting me buy it back without pressure of re payment.

To @rsingler for taking the time to figure out the tricks and tips to tune it.

To @James79 for making the adjuster and having a go at a wider exhaust, I'll buy one off you for sure.

Stomachache commencing, crow tastes bad.

Thank you to all who helped. It's a great reg.

Take care
Simon

Crow doesn’t taste bad after soaking in brine, pressure helps.

 

[lexvil]

Very happy it all worked out, mine is about to go out again this morning.