My machine has been getting noisier and noisier and I have felt for a couple of months that it wasn't working up to speed, so to speak.
I bought a refurb older model off of a web site, (550 Resmed System One) which doesn't have quite all the features the 57x (not sure exact model) and for the past three nights I have slept like a log in the forest.
Took the old one to the DME I bought it through (got gouged big time, btw) and they won''t do any warranty work. For a charge, they will send it off to the factory. Then, come to find out, this particular machine falls into a serial number group that has been under recall for just under two years and they knew about it. Going to be an interesting conversation with the local "cpap liaison" from their store come tomorrow.