Desperate zombie tears into Respironics 750P blower

[Doesheah]

Update - The cause of my 750P malfunction may not have been the blower at all! Skip to my Nov. 3 update below for the latest information.

Hi all. I began sleep apnea therapy in 2011 with a Respironics 750P. This keeps me from being zombie-like. I have logged 13,000 hours and have been quite happy and dependent on this machine. It had been very reliable until a few weeks ago when it began shutting off inexplicably. At some point during the past year, a slight wheeze sound gradually built up so as to become noticeable. The wheeze would come from the machine with every breath at the point where exhalation was ending and inhalation was about to begin. It was never loud enough to disturb my sleep or be heard from an adjoining room. I do change the micron filter from time to time but not with any regularity.

At first, the shutting-off seemed to be a one-time event and I have the machine set for auto-start so I blamed the event on a power glitch. Eventually, the symptom began to happen more often and I began to think of other possible causes. The SD card had over 600 files on it and I wondered if it was running out of write cycles. I copied all files to a new SD card but the symptom remained. I opened the machine and found some gray powdery deposits on the vanes of the blower impeller and the leading edges of the vanes inside the venturi tube. I cleaned these deposits with alcohol, cotton swabs and dust-off spray. I blew a little into the pressure sensor ports as well. After that, the machine seemed to work better. The wheeze was still there but at least the machine wasn't shutting off. I have neighbors who heat with wood burning stoves and one neighbor who burns his trash. There are also the nanometer-sized particles being sprayed into the atmosphere by our silent geoengineering friends. The micron filter won't stop nanometer-sized particles. Your best defense against this is to employ electrostatic air filtration but I haven't done so as yet.

The trouble came back with a vengeance two nights ago at 1AM. The machine began shutting off every 15 minutes. After this happens three times, the machine will give up and not restart. A continuous double-beep is heard and the display indicates "service needed". Pulling the power cord briefly will reset the error and the machine can be restarted but on this particular evening, the symptom continued to accelerate until it got to a point where the power cord had to be pulled every 15 minutes! These machines can run without an SD card, so I removed it. No difference. I removed the filter. No difference. I keep a 12 volt car battery in the room for emergencies and powered the machine from the battery. No difference.

I have considerable electronic and mechanical skills, so I took the machine with me to look at after work. At this point, I have nothing to lose by taking a closer look at the blower. There was a slim chance I might be able to get some lubricant into the bearings. The label on the blower says Respironics P/N 1071170. I can't find anyone on the internet selling these. Respironics wants me to buy a new 60 series machine. I'd wager the new machines have the same blower. Someone please prove me wrong. The blower bottom cover comes off easily with several screws, revealing the impeller. On top of the blower is a plastic cap which pries off easily. Beneath the cap, an aluminum cover is revealed, which is secured with three screws. At the center is a smaller brass disc permanently attached to the motor shaft. This disc had been drilled in one spot for dynamic balancing, I suppose. The aluminum cover isn't going to come off until the brass disc is removed. The impeller on the bottom does not seem to be removable. I tried applying torque in both directions, thinking it might unscrew. Nope. Next, I tried prying on the brass disc. It popped up about 1MM but the motor shaft moved with it and the impeller moved 1MM closer to the motor housing. I'm sure impeller position is critical, so I pushed the brass disc back down and it moved back to where it was. I don't think I've done any harm yet since the impeller still rotates freely with no gritty feel. Next, I tried heating the brass disc with a 120 watt soldering iron. This made it loose enough to pry off without moving the motor shaft. There was Loctite on this end of the motor shaft. Removing the top aluminum cover required some effort because the underside has a bore which supports the outer race of the top ball bearing. It is a light interference-fit. There is a spring washer in this bore to eliminate end-play in the motor shaft.

Now the interior of the motor can be inspected. It seems to be a three phase stator with a rare earth magnet as the rotor. The wires from the two-pin plug disappear into the stator windings and I guess these must go to a pulse generator coil. The main board must be synthesizing a variable frequency three phase drive signal to power the motor at variable speeds. The pulse generator must be providing feedback to the main board for counting motor revolutions. My hypothesis is that the motor was dragging just enough for the pulse count to be outside of allowable tolerances. It might also be possible, the motor could not reach the maximum speeds required for pressure pulses. Thirdly, the magnetic rotor could be gradually losing some of its magnetic force. These bearings did not feel like extreme wear had set-in yet. They have dust shields on them. Mind you, I can now touch the top bearing and I can see a little bit of the bottom bearing. Attempting to use a bearing puller on the top bearing would destroy it. The bottom bearing cannot be removed until a method is devised for removing the impeller (if that is even possible).

My best chance of getting any sleep on this particular evening of September 12th. is to stop here and put the blower back together. Before reassembling, I put two drops of synthetic "Liquid Bearings" clock oil on top of each bearing, hoping some might seep under the dust shields. The oil is odorless and this motor is cooled by conduction through the top aluminum cover. The brass disc went back on after some heat and light pressure was applied to it.

I'm very happy to report, the machine ran like new last night. The wheeze is even gone. I must have gotten lucky between the lubrication and possible realignment of the bearing races. There was no oily smell. When the bearings eventually fail, I'm afraid rebuilding will not be an option. At least I can begin the process of getting another machine and maybe a reader of this forum can point us toward a source of replacement blowers. This experience has taught me, most mechanically inclined sleep-apnea sufferers with a set of Torx drivers should be able to change out a blower. Opening the motor and oiling it is likely to have a success rate of less than 100%. Time will tell how permanent this fix will turn out to be.

[Julie]

Secondwindcpap.com - very good to deal with and they may not require a script for machines as other places do (outside of Craig's list). They recon machines and have a variety of good ones.

[palerider]

I'm guessing that your problem wasn't the blower, but rather the dodgy connection of the pressure and flow sensors to the air tube, that's a known trouble spot on the 50 series... along with melting plugs on the humidifier connection due to undersized plug connectors.

acbio.com may be able to set you up with a replacement blower, though.

grayghost4 can likely set you up with another machine, you'd likely enjoy the superior engineering of the resmed s9 or air10 machines.

[Sir NoddinOff]

I'm guessing that your problem wasn't the blower, but rather the dodgy connection of the pressure and flow sensors to the air tube, that's a known trouble spot on the 50 series... along with melting plugs on the humidifier connection due to undersized plug connectors.

acbio.com may be able to set you up with a replacement blower, though.

grayghost4 can likely set you up with another machine, you'd likely enjoy the superior engineering of the resmed s9 or air10 machines.

I agree. For backups etc I always avoid early x50 models and look for the updated x60 versions for the reasons given above. There are some kludges/fixes around for the 50 series here at CPAPtalk, like you so ably found out with the bearings. How long's it going to last tho? Send it to Accurate BioMed, I know for a fact that PR often replaces the x50 series:
http://www.acbio.com/cpap-repair/

[Bill44133]

I'm guessing that your problem wasn't the blower, but rather the dodgy connection of the pressure and flow sensors to the air tube, that's a known trouble spot on the 50 series... along with melting plugs on the humidifier connection due to undersized plug connectors.

acbio.com may be able to set you up with a replacement blower, though.

grayghost4 can likely set you up with another machine, you'd likely enjoy the superior engineering of the resmed s9 or air10 machines.

I agree. For backups etc I always avoid early x50 models and look for the updated x60 versions for the reasons given above. There are some kludges/fixes around for the 50 series here at CPAPtalk, like you so ably found out with the bearings. How long's it going to last tho? Send it to Accurate BioMedical.

I agree Accurate Biomedical is the BEST!! Ian the owner is a forum member here. His name here is accurate. You might try send him a message.

He repaired my 750 machine and it works like a charm now. He was very reasonable and service was the best.

I wish you well..

[Sir NoddinOff]

I'm guessing that your problem wasn't the blower, but rather the dodgy connection of the pressure and flow sensors to the air tube, that's a known trouble spot on the 50 series... along with melting plugs on the humidifier connection due to undersized plug connectors.

acbio.com may be able to set you up with a replacement blower, though.

grayghost4 can likely set you up with another machine, you'd likely enjoy the superior engineering of the resmed s9 or air10 machines.

I agree. For backups etc I always avoid early x50 models and look for the updated x60 versions for the reasons given above. There are some kludges/fixes around for the 50 series here at CPAPtalk, like you so ably found out with the bearings. How long's it going to last tho? Send it to Accurate BioMedical.

I agree Accurate Biomedical is the BEST!! Ian the owner is a forum member here. His name here is accurate. You might try send him a message.

He repaired my 750 machine and it works like a charm now. He was very reasonable and service was the best.

I wish you well..

Ditto for my experience.

[Doesheah]

To all who responded, I wish to offer my sincerest thanks for pointing me in the right direction for obtaining a backup machine and naming a reliable vendor for the eventual refurbishment my old machine will need.

It's been two weeks since my original post and I'm happy to report my machine has performed flawlessly during this time. It's interesting to hear there are known issues with the connection to the pressure and flow sensors. Prior to working on the blower, I had opened my machine once before to do the cleaning I mentioned. I saw the silicone rubber piece that couples the sensors to the air tube. It came off with the circuit board and the fit felt pretty tight on both the sensors and the air tube. I cleaned the coupling with an alcohol swab at that time. The two plastic studs which support the circuit board do have enough 'give' to allow a small lateral movement of the circuit board, so I imagine the simple act of pressing on the SD card could deflect the main circuit board enough to cause the silicone coupling to leak. If the wheezing sound ever comes back, I'll examine that silicone coupling much more closely.

At this point, it is difficult to conclude whether it was the blower, the silicone coupling or something else which was causing the malfunction.

[yaconsult]

Is there any empty hole next to where the tubes connect to the sensor with a plastic post under the hole? If so, I had the same problem with my 550P and a self-tapping screw of the appropriate size solves the problem permanently. If you search the forum, you can find several threads showing the repair complete with photos. Good luck! Without the screw, it may fail again at some point in the future. Curse the asshole who decided that that screw wasn't needed and removed it from the parts list!

[palerider]

I had the same problem with my 550P and a self-tapping screw of the appropriate size solves the problem permanently. ... Curse the asshole who decided that that screw wasn't needed and removed it from the parts list!

I wouldn't say "permanently" since the issue has shown up in the 60 series, which does have a screw there.

removed from what parts list?

[baja05]

There is a list of venders on a thread if you want to see if you have a local company. It's the blower, I bet it has error codes 22, 24, or 30. Early Respironics for blower issues.

[Doesheah]

Thanks for the prompt replies!

Yaconsult - There was definitely no self-tapping screw there. This machine is early 2011 vintage. I'll check for the hole when my backup machine arrives. Your 550P was aptly named. 5:50 is about the time I awaken to 'P'.

Baja05 - I'll try checking the clinician menu to see if any error codes were logged. Or do I need special software to access the codes? I'll search this forum for an explanation of the codes and also for names of some vendors local to Hyde Park, NY.

Palerider - Practically all manufactured products have a Bill Of Material. Someone would have had to delete the screw from the BOM. There is usually a reason for doing so. I doubt it was the cost of a screw. Whether the screw causes a problem or cures it remains to be seen. I'd be glad to try adding one if my problem persists.

[palerider]

Palerider - Practically all manufactured products have a Bill Of Material. Someone would have had to delete the screw from the BOM. There is usually a reason for doing so.

why would someone delete something that was never on the BOM?

why do you, and yaconsult ASS-U-ME that there was some magical screw designated to be put there in version one of the device simply because there was a screw in version 2 of the device?

don't designs hopefully tend to evolve over time, and improve from one generation to the next?

isn't it much more likely that when they revised the 50 series into the 60 series, they realized their faulty engineering in version one (50 series) and did something to hopefully make it better? (using a screw to hold down the board instead of a boss from the top cover?)

[Doesheah]

Palerider - You are right. I should not have assumed any of the 750P models ever left the factory with a screw securing the silicone pressure sensor coupling. It is curious that both earlier and later models evidently have the screw. I've been in the electronics repair business for many years and manufacturers seldom ever admit to having knowledge of product defects. "We've never seen that before" is the usual excuse. Now I'm really curious whether my machine has the same molded plastic parts as preceding and subsequent models. If the engineers decided to put the screw back into the 60 series product, they probably had a good reason for doing so.

I'm still waiting for someone to reveal the blower part number in the 60 series machine.

The day Philips sends a replacement machine with a letter of apology is the day I will shut up. Until that happens, I won't pull any punches during the course of this critique.If the machines life expectancy is only 5 years, the real cost of owning one is $480 per year based on the $2400.00 retail selling price. At least the Philips stock price has gone up 1.13 Euro since the date of my OP.

[palerider]

Palerider - You are right. I should not have assumed any of the 750P models ever left the factory with a screw securing the silicone pressure sensor coupling. It is curious that both earlier and later models evidently have the screw.

there is no earlier model. before the system one "50 series" there was the M series, which was wholly and completely different. the x50p line was the first, the x60p line was the last.

Now I'm really curious whether my machine has the same molded plastic parts as preceding

to reiterate, the preceding model looked like this:

I'm still waiting for someone to reveal the blower part number in the 60 series machine.

it's probably the same.

The day Philips sends a replacement machine with a letter of apology is the day I will shut up. Until that happens, I won't pull any punches during the course of this critique.If the machines life expectancy is only 5 years, the real cost of owning one is $480 per year based on the $2400.00 retail selling price. At least the Philips stock price has gone up 1.13 Euro since the date of my OP.

do hold your breath waiting on that. who pays retail?

as far as I'm concerned, it's a poorly engineered piece of kit, the reports of burned humidifier connections from underspec'd (or marginally spec'd) connectors attests to that... you open it up and it just... feels... cheap.

[Doesheah]

Hi all,

It's been a little over 7 weeks since my original post. My machine had been behaving pretty well for the most part until a few days ago when the original symptom returned (shutting down, continuous double beep and displaying 'service needed'). I had not touched the SD card until a few days ago and it is beginning to look like I may have been a bit too hasty blaming the blower as the cause of this symptom. Another reader had alerted me to some other known issues with the Philips 750P, one of them being the integrity of the seals in a small silicone rubber coupling. This coupling makes three connections between the pressure, flow sensors and the air tube. The sensors are on the underside of the main board. This board is loosely held in place by two plastic bosses on the blower housing and two plastic bosses on the underside of the top plastic cover. There are three small nipples on the air tube and three similar nipples on the sensors. The silicone coupling makes a friction fit over these nipples.

Since the main board is not rigidly held in place, it is possible for it to move both laterally and vertically by a small amount which can disturb the sealing surfaces of the silicone coupling. I made a measurement of the main board lateral motion using a dial indicator banked off the rear of the lower machine housing. The probe was placed in contact with the side of the control knob. I saw almost .010" of movement from front to back while inward pressure was applied to the SD card. I'd have to drill a hole through the top cover to measure main board vertical movement. There is no access to the top upper right corner of the main board where the sensors are. I might try probing the top of the control knob even though it is some distance from the sensors.

I opened the machine and observed a hole in the main board next to the sensors. There is a plastic boss beneath this hole, emerging from the blower housing. The hole in the boss is sized to accept a No. 8 self-tapping screw. It had never had a screw in it. I decided to place a film of Rhodorsil vacuum grease on the sealing surfaces of the silicone coupling. In addition, I installed a suitably sized self-tapping screw with a fiber washer under the screw head.

I will let you know how the machine behaves after a few days of operation including frequent removal of the SD card.