OT: Looking for a DC PSU

[oceansoul]

Slightly off topic, but im wondering if anyone can help.
I have a PSU which has 24VDC input then out puts -12VDC 0VDC and +12VDC. This has failed and is giving out aprox -3.8VDC and +4VDC. This supplies a specific (anicent) serial line driver which we cannot replace at this time (trust me ive tried). So i need to replace the PSU to get it working again.

Does anyone know where i can find such a 12-0-12 PSU? I have tried RS but cant seem to find anything suitable. I suspect that some thing could be made up, but im not sure how. Current is aprox 700mA.

 

[bernardgreen]

http://www.calex.co.uk/product/power-conversion/dcdc-power-converters/dcdc-converters/

Two 24S12.1250BR converters will each give 1.25 amps at 12 volt,

But if the 700 mA current on the 24 volt supply then one 12D12.416EW will give +/- 12 at 416 mA

 

[endecotp]

RS have for example:

http://uk.rs-online.com/web/p/isolated-dc-dc-converters/7813377/

If you start here you can add filters including +/- 12 V output etc. etc:

http://uk.rs-online.com/web/c/power...s/dc-dc-converters/isolated-dc-dc-converters/

 

[oceansoul]

So use two of them and tie the 0V rail together? For some reason i'm really struggling to grasp this?
I found this voltage divider using resistors but i dont seem to "get it". Surely the top rail will give =24VDC, the middle +12VDC and the bottom 0V.

 

[endecotp]

Or if you prefer screw terminals:

http://www.digikey.co.uk/product-detail/en/cui-inc/PYB30-Q48-D12-U/102-3266-ND/4477524

lots of other options at Digikey.

 

[endecotp]

So use two of them and tie the 0V rail together? For some reason i'm really struggling to grasp this?
I found this voltage divider using resistors but i dont seem to "get it". Surely the top rail will give =24VDC, the middle +12VDC and the bottom 0V.

No. That only works if you don't draw any current from the outputs. Not what you want (but not for the reason you suggest).

 

[oceansoul]

Thanks guys. Found what i'm after on RS now. I wasn't looking for the right thing, but have now.

 

[flameport]

Surely the top rail will give =24VDC, the middle +12VDC and the bottom 0V.

It would if you considered the bottom rail as 0V.
If you consider the middle as 0V, the others are +12 and -12.
Or if the top one is 0V, you have -12 and -24.

0V is just a reference point you are choosing to be zero, against which the other voltages are measured.