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[News] RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
(07-05-2021, 07:20 PM)qwerty42 Wrote: Hi all, your local mechanical & aerospace engineer here. I took my Dreamstation apart today and now have definitive info about my earlier guesses:
  • The sensor labeled 1 is indeed a humidity sensor. Labeled SHT20 D6UYU, it's a Sensirion humidity sensor IC which also measures temperature.
  • The sensor labeled 2 is indeed a differential pressure sensor (Sensirion SDP703-02), and I've confirmed it's measuring mass flow rate. In the plastic "tank" where these pressure ports connect, there is a white plastic grating which acts as a slight flow restrictor. By measuring the pressure delta across this restriction, the machine can calculate mass air flow rate. It is actually capable of bi-directional flow rate measurement as long as they coded their firmware to calculate both directions.
  • The sensor labeled 3 is indeed another differential pressure sensor (C02069 NPA1711008). The part number appears to be a specialty configuration, but it's based on a readily available Amphenol NOVASensor pressure sensor. This one is measuring the output pressure of the blower (meaning your mask and hose pressure too), and is referencing it to ambient atmospheric pressure through the second port.
Based on my teardown and inspection, I can say with a high degree of confidence:
  1. The foam does *not* need to be in the unit for any of these sensors to work. However, the void left by removing the foam might introduce a bit of extra turbulence/vorticity in the flow, which could make the mass airflow sensor less accurate. My gut feeling here is that it probably won't make a big enough difference to matter, but I can't say this definitively without a lot more involved analysis and/or testing.
  2. Any cutouts made to remove the foam upstream of the differential sensor (the pair of side-by-side ports where sensor #2 connects) must be sealed back up, airtight, for the sensor to measure mass air flow correctly. Ideally, any cutouts on the downstream side should be covered too, but they shouldn't make any difference to this sensor even if they aren't.
  3. If you cut into the chamber to remove the foam, it'd be best to keep your cuts well away from that middle section where sensor #2 plugs in, because rough edges there could create flow trips which might affect the accuracy of that flow sensor's calibration.

I removed my foam yesterday and drilled three 1/2 inch holes to get it out.  I am thinking hard about going back into the machine and plugging up holes with hot glue or something but the machine seemed to work as normal/my AHI measured by the machine was typical too., (I did not have time to look at it in OSCAR).

Has there been more talk related to how important it is to plug up the holes if they are on the "inside" in the sealed part of the plastic box? I love my CPAP and it was bothering me every night before going to bed thinking about the possible risk of the foam (be it likely pretty small as I don't use ozone/don't every keep it in a high heat/humidity setting).  Figuring it will be many months and possibly a year or more.... I told myself just yank that foam out of there and stop procrastinating.

Thanks in advance!
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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
QWERTY & brian:

These are great posts… Probably the best I’ve read on here on WHAT TO DO, Rather than the plethora of hand ringing and anger posts that seem to permeate here. It’s time we put some HOW TO FIX/SOLUTIONS here instead of “who did this and why”? I really don’t care how it happened, it just has happened. Yeah Philips sucks… Now …..moving on to a solution…

I think it would really help if we could get some clear definitive photos of the inside of these machines and step-by-step what to do complete with arrows /circles because there are a lot of us that are OK with this operation if I knew what I was doing. I’m completely familiar with small screwdrivers/Dremel tools, micro drill bits, hot glue, epoxies‘s and other small tools to get this done, If I knew exactly what to do. It would even help if we put a link with a list of the exact Products we should buy in making this modification i.e. glues sealants, epoxies, maybe even the Dremel tool bit, etc. etc.… Then we can put this as a completely separate post as a sticky up top for people that want to tackle this. My brother has a dream station sitting on the shelf that I would love to fix.

I’m interested in a hardcopy post that I could print out, not a YouTube video. I have done engine tear downs on cars and boats via YouTube, and find it much easier to do the same operation following a shop manual with clear, close-up pics instead of video.
Glen in Ft Lauderdale

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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
brianc18t Online You failed to read my response and HIS replay to my pointing out that may not work: Look here

http://www.apneaboard.com/forums/Thread-...#pid401499

Read from Post 513 on and I think you will see what should be done.OK?

Good luck.

Rich
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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
If I may make a suggestion.
Start a PR De-foaming thread. it will make it easier for users to find it.
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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
Yes that’s my point. Start a completely separate thread, and after refining it , have the mods sticky it at the top so everybody can reference it.
Glen in Ft Lauderdale

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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
Glen, just be aware that sticky space is at a premium. Very little goes there.
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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
(07-22-2021, 05:04 PM)Gideon Wrote: If I may make a suggestion.
Start a PR De-foaming thread.  it will make it easier for users to find it.

I would if and when I no longer need to wait a day to make a post or a replay.

Rich
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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
I can’t think of anything more important right now than a sticky on how to mod these machines correctly……. Make the space…
Glen in Ft Lauderdale

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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
We still aren't sure how wide spread this issue is. I wonder if using a bacteria filter to capture any possible particles might not be a simpler solution.
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RE: RECALL THREAD-- IMPORTANT PHILIPS DREAMSTATION & SYSTEM ONE USERS
(07-22-2021, 05:01 PM)racprops Wrote: brianc18t Online  You failed to read my response and HIS replay to my pointing out that may not work:  Look here

http://www.apneaboard.com/forums/Thread-...#pid401499

Read from Post 513 on and I think you will see what should be done.OK?

Good luck.

Rich

Affirmative, thank you from redirecting me from my failure.  I feel so lazy not reading all 88 pages in this post.  Few things grind my gears more than people not doing their homework!
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