Toroid series and parallel secondaries

[warpie]

Ok, I'll be as quick as possible...  ;D

Can I get +/- 28Vdc from a 30VA 15V+15V 1A toroid, and if so how?

I connected the secondaries in series and I could only get a maximum of +/- 22Vdc.
I know is simple but couldn't find any info around  :

 

[gridcurrent]

Sure.  With half wave rectification and low current draw.

 

[warpie]

so, is it not recommended?
Even down to 500mA should be alright for my project.
How do I wire it?

 

[Harpo]

secondaries wired in series, center tab not used.

 

[abbey road d enfer]

Alternative solution
But in all cases, you'll need large caps and the xfmr will be stressed. Asking 500mA from a voltage doubler is asking 1Amp from the transformer. And single-wave rectification is hard on rectification transients and losses.
I wouldn't do it. Get a suitable xfmr.

 

[warpie]

thank you both for the diagrams 

So, it looks like getting another transformer is the best solution.

Will something like this do for my purpose (+/- 28V)?
I'm using the JLM Audio AC/DC PSU if it matters...

ENCAPSULAT TOROID 50VA 25V+25V 1A(RC)
http://www.rapidonline.com/productinfo.aspx?tier1=Electrical+%26+Power&tier2=Transformers&tier3=Toroidal&tier4=Encapsulated+toroidal+transformers&moduleno=72657

I hope to buy the right one this time  :

 

[abbey road d enfer]

This one should give approximately +/- 35VDC at 700mAmp, which should be correct for regulating at +/-28. That's 7V across the regs. I don't know what the JLM regs are, but they should be fine with 7v drop.

 

[warpie]

thanks d enfer,

the jlm has two LM317s and one 377 so 7v drop shouldn't be a problem.
I'll try it.

thank you all for your help!
w.