Yes.
You cannot get separate ±15Vdc outputs from one two-wire AC source.
To get plus 15Vdc and minus 15Vdc (to ground) you need a separate 15VAC source to ground for each voltage.
This can be done with two separate AC sources, or a 30VAC center-tapped output transformer with the center tap going to ground.

How does this work then? This is the design I used but with 2 x 1000mf caps.

http://musicfromouterspace.com/anal...PPLY/wall wart supply with load resistors.gif

 

Hello,

Have a look at the pages 8,9 and 10 of the attached PDF.
It shows the rectification (but without a capacitor)
The circuit with a capacitor is shows from the pages 31 and on.

Bertus

 

How does this work then? This is the design I used but with 2 x 1000mf caps.

Yes, that will work.
I wasn't thinking about using half wave rectification.
But note that the transformer will not like it (get hot) if you draw a lot more current from one output than the other, due to the high DC current this causes in the transformer, which can saturate the core.

 

Yes, that will work.
I wasn't thinking about using half wave rectification.
But note that the transformer will not like it (get hot) if you draw a lot more current from one output than the other, due to the high DC current this causes in the transformer, which can saturate the core.

Ok so this setup should work. Can you advise about how to wire this up because it's not working as it should and the regulators are getting very hot, very quickly, I cannot even touch them, so there's obviously something going wrong somewhere. The AC-AC wall adapter has tip and sleeve connections, (it's labeled as, pos and neg). The way I currently have it setup is; positive or tip is being sent through 2 wires. 1 of those wires is going to the positive rectification and the other is going to negative rectification diode. I am then using the sleeve or negative connection of the adapter to go to ground. Is this correct?

 

Hello,

Have a look at the pages 8,9 and 10 of the attached PDF.
It shows the rectification (but without a capacitor)
The circuit with a capacitor is shows from the pages 31 and on.

Bertus

Thanks for that Bertus, it looks like a good resource to have at hand.

 

The way I currently have it setup is; positive or tip is being sent through 2 wires.

Why two wires?
Aren't they both at the same voltage?

 

Why two wires?
Aren't they both at the same voltage?

That's how it is done on the schematic. I also made the circuit on strip board and didn't link the input diodes onto 1 strip. So the wire has to be split in order to go to pos and neg diodes. Hopefully you know what I mean.

 

Then if they are heating up, you likely have a wiring error.
Double check the pinouts on the two regulators.

 

Then if they are heating up, you likely have a wiring error.
Double check the pinouts on the two regulators.

Hi Crutschow. I checked everything with a continuity meter and for some reason there were sections being shorted to ground, so after rebuilding it and having the same issue I realised I had a bad tantalum cap with both legs shorted together. I replaced that cap and then everything worked on the continuity meter, however, when I plugged it in my synth started to smoke and and a really weird smell. One of the tantalums was burning up. It turns out after doing a little bit of research that these tantalum caps are polarised, I was completely unaware of this important point. Anyway, I ended up buying an assembled board that works with the synth. So for now I think I'll stay away from assembling my own power supplies haha

 

Yes, tantalums are electrolytic capacitors, the same as the aluminum types, and are thus polarized.