What deco algorithmn and settings do you use?

silent running

I use HE RGBM CF 0 for shallower, minimal deco dives and CF 1 for hypoxic dil, longer deco dives. With Naui RGBM tables and timer for backup -Andy

trob09

A sampling of a few recent dives:

- Dive 1 - in the last 10 minutes of a 220' dive, PO2 reading drop from 1.4ish to 0.1ish for no reason (I was essentially stationary decoing on a rock in 1000 islands). HUD readings tracked with the handset. Bail out to OC o2, finish dive.
- Dive 2 - HUD went dead 15 minutes into the dive. Handset worked as expected. I called the dive
(turn off unit, turn on unit, calibrate, double check, triple check)
- Dive 3 every thing went fine 110' 85 minute run time
- Dive 4 everything went fine 220' 95 minute run time
- Dive 5 in the middle of my pre-breathe, PO2 readings went from .7 to 0.0 with no warning (I had just calibrated the head prior to the dive) HUD readings remained at .7 Solenoid doesn't fire at this point, even though it had been working before that in the pre-breathe. Flooding the loop with O2 generates a .4 PO2 on the handset and a 1.0 on the HUD.- called the dive before getting into the water.

When it works, it works very well. Profile generation matches what I expect to see. The problem is and has been that I will get significant variation in PO2 reading from one minute to the next with no apparent reason. HUD and handset will sometimes agree on the PO2 and sometimes won't. Handset and HUD will each occasionally quit working for no apparent reason (and then start working again later). This degredation started in February and has gotten progressively worse.

In the end, I have decreasing confidence that the PO2 readings I see on the HUD/Handset are accurate or will remain accurate. Every dive is marked with an inordinate amount of dil flushing to verify that the PO2 readings are accurate. I've sat out of 1/3 of the dives on recent trips because of these problems.

Is it the board? Is it the software? is it the assembly? is it the wiring? I don't have a clue. I do know I'm done messing with it.

Tim

decoweenie

Have you tried to get it sorted out with ISC or Bruce directly ?

I guess you probably have, and they are probably passing the respobsibility back and forth ?

I don't know what the issue is, but just guessing from reading some of the blame issue discussion about why Shearwater is no longer offered with the Meg...

I am interested in finding out your problem because I am in the process of getting a Shearwater controller fitted to one of my YBOD lids.

I sincerely hope the HH-Meg option will solve your problem instead of trading one mess for another.

__________________
"...after a while you get bored offering advice to a bull that like to keep butting the fence with its head rather than walking through the open gate..."

- Rebreather World PM

trob09

They worked flawlessly for about a year, and then the problems started. Frankly, I'm done trying to figure out what's wrong.

Leon's answer is Apecs 2. I haven't spoken to Bruce directly about it, but I know he will replace the ISC shearwater with his replacement unit for a discount. I don't find the replacement shearwater all that attractive (handset seems excessively large/brick-like and I don't like the exterior brick for the HUD) and the no deco Apecs 2 doesn't quite do it for me. Maybe as a backup....

watching (closely) a half-dozen others who have the hammerhead, I feel pretty good about it as the replacement.

bgpartri

Tim,

That is the classic failure. It's the way mine failed.

The O2 connector is on the edge of the circuit board and it's the first thing that gets wet when the case leaks.

It was one of the first hints of what the problem was. The computer and HUD use different processors, different compilers, and different batteries. The only thing that they have in common is the enclosure, and in the enclosure the thing that they share is the O2 connector. When both O2 readings fail at the same time, it's a pretty good indicator of where the problem is.

You can fix it for a while by getting it hot with a heat gun to dry it out, but there is no proper seal so it's doomed.

I am told that the later ones were coated in conformal coating and lifted 1/4" off the mounting plate so the potting compound enveloped them. They apparently work fine.

__________________
http://www.rebreather.ca

Good judgement comes from experience, and experience comes from bad judgement.

trob09

Thanks for the note Bruce.

Mine was apparently one of the last 3 or 4 units that Leon/Steve replaced. I had an early-on failure as well, the handset went blank & I couldn't get it to start. ISC replaced the potted board and all was well for about a year. My understanding was that the replacement had the coating & deeper potting that you mention.

As I say, when it worked, it worked very well. I was quite pleased with the simplicity of the shearwater unit. Unfortunately, it has gotten to the point where I don't feel I know my PO2.

I think I sorta know, maybe.

bgpartri

Apparently not, or you wouldn't have the problem.

You should definitely not be diving that computer. With water on the O2 connector, the readings are not reliable.

__________________
http://www.rebreather.ca

Good judgement comes from experience, and experience comes from bad judgement.

trob09

Like I said earlier, I'm done messing with it so it doesn't really matter anymore.

Exactly my thoughts.

JPJones

Hammer Head 35 95 most of the time.

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