10-08-2014, 09:44 AM
(This post was last modified: 10-08-2014, 09:47 AM by justMongo.)
(10-08-2014, 09:12 AM)Sumwhatinterested Wrote:
(10-08-2014, 08:28 AM)justMongo Wrote: Good Morning
(10-08-2014, 05:39 AM)Sumwhatinterested Wrote: Hi Mongo,
I connected the S8 to 12 volts to try it out because it has a normally 12 volt plug pictured on the Resmed adapter. I learned later that the center pin is negative unlike most automotive accessories. May I ask where or how you determined that the S8 DC input is 24 volts?
Thanks for the reminder, I guess I forgot my basics.
But now I see another way to post a picture of the board in question, because of your reply.
Thanks for your effort.
I'd like to see the component location your referring to.
An S9 runs off 24 VDC for both the blower unit and the humidifier.
The S8 uses the AC voltage to heat the humidifier. It has an SCR that is pulse modulated to control the heater plate.
The designer may have relied on the plug to protect against reverse polarity.
I would have protected it with a pair of Schottky diodes -- low forward drop.
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
10-08-2014, 07:45 PM
(This post was last modified: 10-08-2014, 07:46 PM by Sumwhatinterested.)
With the AC cord plugged in, I do get a 12vdc signal coming from the power pins of the supply. This is coming through the terminals at the main board.
As I look at my bottom label, I recall now why I used 12v, it's because it does take 12v! There must be a few different versions of the S8? I would like to post images, however, I have not reached that magic 8 post cap limit.
This is a ResMed AutoSet Vantage BTW.
Hi everyone, I know this is an old post but here's the solution if anyone needs it. I did the same thing. We had a cyclone come through our area and we lost power for 9 days. I figured I would run my machine on DC since I was not sleeping so well and it has an input for it.
Here is the stupid part: Res Med have reversed the polarity for the 12V DC input compared to the standard for just about everything else on the planet. I fail to understand why!!! Anyway, if you make up your own lead with centre pin positive you will damage your unit. That was me.
I am lost by the reference to 24v in this thread. The Res Med S8 is a 12v unit all the way through. No 24v at all.
So, I damaged my unit by hooking up to 12v with the centre pin positive. That killed it and after that it did not work at all. First I tested the power supply. All good and producing a perfect 12v DC to the main PCB. So now it was time to tackle the top PCB. Although it looks rather daunting, the fix is very easy.
There is a white ceramic fuse situated between where the six 12v DC pins engage with the PCB and the back lit screen. The position label is F1A (if I remember correctly). This is a 5amp fuse and will have been blown by the reversed polarity. If you place a pair of pointy nose pliers across the two ends of this fuse, with the unit plugged into power, it should light up and come to life. If it does, you have confirmed your problem.
I left the current fuse in place and soldered and replacement over top and a bit off to the side so as to not get in the road of the buttons. My machine now works again on both 240v AC and 12v DC as it should.
Hope that helps someone. I reckon a few people will have made this mistake.