Ron, I think the difference is that I assumed that he is using a center tapped transformer and just neglected to show the center tap connected to GND. If it is not a center tapped arrangement then the -ve voltage will be lower. I have not drawn in the C.T and transformer, but set up the incoming AC to act in such a way. Here I have taken the effort to use a transformer and simulated both conditions.

The one is a 12.6V + 12.6V and the last a 12.6V only.

Originally Posted by TheOne

Ron, I think the difference is that I assumed that he is using a center tapped transformer and just neglected to show the center tap connected to GND. If it is not a center tapped arrangement then the -ve voltage will be lower. I have not drawn in the C.T and transformer, but set up the incoming AC to act in such a way.

NO! - the centre tap must not be connected to ground, it's a bridge retifier circuit, the centre tap isn't used - giving the full 12.6V from both windings to feed a single rail. His original diagram was drawn quite correctly.

Originally Posted by Sebi

This cct also work with one bridge.

Yes, a standard fullwave rectifier, using a centre tapped transformer (or in your diagram two transformers), generating split supplies.

But this wasn't what he wanted to do.

But his original circuit won't work with one winding at 12.6V (unless he removes the GND from the bridge and connects it as a centertap 12.6V+12.6V) as the -ve voltage is then too low to feed the -ve 12V regulator as Ron also found in his first simulation. Will only work with a doubler setup. One of the first posts say something about a center tap transformer on the diagram. :?

Sebi, yes! (fixed), like I said the -ve side will be 1/2 wave doubler and the +ve side standard full wave.

I was thinking in terms of a light or no load and the danger of max input voltage to the regulator which is -40V. The -ve section will still work as a 1/2 wave voltage doubler where the top will be normal full wave rectification.