+- 30V from two dual +-15 supplies? - diyAudio
 +- 30V from two dual +-15 supplies?
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 1st August 2008, 08:22 PM #1 diyAudio Member   Join Date: Feb 2004 Location: Silicon Valley +- 30V from two dual +-15 supplies? Greetings, I have two surplus DC regulated power supplies; each of them has dual outputs of +-15V. I need one +-30V supply. I'm thinking about the following. In each PS tie the 0s of each output, this should give two supplies: +30 and -30, depending on what will be further referenced as 0. Then tie the 0s of these supplies to obtain +-30V PS. Are there any caveats in this arrangement? Thanks!
 1st August 2008, 09:17 PM #2 Did it Himself diyAudio Member     Join Date: Nov 2003 Location: Gloucestershire, England, UK Slightly confused by your words, but basically you need to connect the supplies in series with each other - negative of the 'upper' one to positive of the 'lower' one then this junction becomes your 0V poiint. But be sure to see first if any of the outputs is connected to earth. If it is then you can't do this as you will end up shorting one of the sides. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
 1st August 2008, 09:59 PM #3 diyAudio Member   Join Date: Feb 2004 Location: Silicon Valley OK, thanks!
diyAudio Member

Join Date: Feb 2004
Location: Silicon Valley
Hi richie00boy,

I managed to find the schematics of the outputs. It shows that the +/-15 are connected sharing a common return, so I can obtain 30V straight from +out and -out. So can I connect two such supplies in series for +/-30V?

Thanks!
Attached Images
 ps.jpg (8.9 KB, 153 views)

 4th August 2008, 08:15 PM #5 Did it Himself diyAudio Member     Join Date: Nov 2003 Location: Gloucestershire, England, UK Need to the the whole schematic! My concern is that COM terminal, it seems to be possibly connected to your +15 0 -15V midpoint. If this is then earthed through the case there may be problems connecting two supplies in series. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
diyAudio Member

Join Date: Feb 2004
Location: Silicon Valley
Hi richie00boy,

This is the full schematics, it doesn't look like the COM is earthed.

Thanks!
Attached Images
 ps_full.jpg (50.9 KB, 149 views)

 4th August 2008, 08:43 PM #7 diyAudio Member   Join Date: Jan 2002 Location: Tyrone Ga. U.S.A. As Richie pointed out it depends on if the common 0 terminal is floating or connected to earth. When you first hook these supplies in seriese you might make this connection through a 1/2w 10ohm resistor or a 1/2A fuse just to be safe.

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