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[Equipment] Looking at S8 circuit board
#1
Hello,

I have accidentally fed 12v in reverse polarity to my S8. From what I can tell, I have not burned any fuses, however I have located a place where the component could have burned away. I notice there are some photos of the S9 board, so if anyone has photos of an S8, I am curious about the component that appears to be in the position marked "PT1". You'll notice the arrow pointing across the opening, I am hoping this means PT1 is referencing those little burned solder terminals to the left of the notch of the green board.

I would like to post a picture, but at the moment, I don't believe I am allowed.

I'm not asking anyone to play electrical engineer, of course, just putting the puzzle back together. If you've had similar experiences, I am always curious of your findings. Thanks in advance.
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#2
S9 and S8 are apples and oranges. Internal supply for S8; power brick for S9.
S8's DC power input is 24 Volts -- why are you connecting 12 V DC?
This Veteran is medicated for your protection.
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#3
Hi Sumwhatinterested,
WELCOME! to the forum.!
Hang in there for more responses to your post and best of luck to you as you continue your CPAP therapy.
trish6hundred
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#4
It seems the s8 does have a AC input and a dc input. As Mongo said it needs their adapter to go from 12 vdc to 24 vdc? It would bypass the humidifier when DC was used. Usually a dc input will have a reverse polarity diode across that input that would clamp the wrong polarity and blow some protection device. If left reversed long enough some times would short that diode also. Hopefully that is what PT1 is and it did it's job before further damage. I have no info or access to any info so your back where you started.
Does it still work with the a/c cord?
I'll leave the Engineering to Mongo but try to help in the repair dept.
Good Luck!

Doc J (despite my nickname I am not a doctor)

Remember to donate to the board if you can, it has helped a lot of people including myself.
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#5
(10-07-2014, 09:00 PM)justMongo Wrote: S9 and S8 are apples and oranges. Internal supply for S8; power brick for S9.
S8's DC power input is 24 Volts -- why are you connecting 12 V DC?

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
(10-07-2014, 10:00 PM)trish6hundred Wrote: Hi Sumwhatinterested,
WELCOME! to the forum.!
Hang in there for more responses to your post and best of luck to you as you continue your CPAP therapy.


Thank you Trish6hundredSmile

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#6
(10-08-2014, 12:04 AM)Doc J Wrote: It seems the s8 does have a AC input and a dc input. As Mongo said it needs their adapter to go from 12 vdc to 24 vdc? It would bypass the humidifier when DC was used. Usually a dc input will have a reverse polarity diode across that input that would clamp the wrong polarity and blow some protection device. If left reversed long enough some times would short that diode also. Hopefully that is what PT1 is and it did it's job before further damage. I have no info or access to any info so your back where you started.
Does it still work with the a/c cord?
I'll leave the Engineering to Mongo but try to help in the repair dept.

Good Morning Doc J,
The unit itself does not light up, however the power supply does provide about 5 volts (if I remember correctly)
at the main board input. Thanks for your reply.

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#7
I just did a search for the s8 and there are still listings showing the unit even though they are no longer for sale. When you look at the specs they say a dc input only for use with their adapter. They didn't say 24 volts dc but I would believe that's what it is. So there would have been issues even if the polarity was correct. I would look for a used one cheap and get an adapter if needing to go dc.
Good Luck!

Doc J (despite my nickname I am not a doctor)

Remember to donate to the board if you can, it has helped a lot of people including myself.
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#8
(10-08-2014, 07:38 AM)Doc J Wrote: I just did a search for the s8 and there are still listings showing the unit even though they are no longer for sale. When you look at the specs they say a dc input only for use with their adapter. They didn't say 24 volts dc but I would believe that's what it is. So there would have been issues even if the polarity was correct. I would look for a used one cheap and get an adapter if needing to go dc.

Hi Doc J,
I have looked at buying another S8 but I 'd like to repair this unit at this time. I believe I'm at the component level and hope to attach a link to a picture of the suspect area on the board.
As to the DC adapter I have successfully run this unit all night using a 400 watt inverter with a 12 volt car battery. The inverter is less money and has other uses. More to follow.
Thanks for your efforts.

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#9
(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
I read the bottom...
[Image: 13SEPT2013004.jpg]
This Veteran is medicated for your protection.
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#10
(10-08-2014, 08:28 AM)justMongo Wrote:
(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
Good Morning
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.


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