with a 12.6-0-12.6 winding ( from the 25.2vac/2A TX ), two diodes for a full wave rectifier, ground the CT to the capacitor's negative rail( 4700 uF/25 volt ). put a resistor between the cap and the diode's cathode's ( the banded end, the other goes to the 12.6 vac ends of the TX winding ). 5R is a good value. make another R-C section with a 3R resistor and terminate with another 4700 uF cap. OUtput ought to be close to the desired 12.6v. Up to 13 is OK.

The 5R ought to be a 5W wire wound. The other R ought to be similar construction. I'll draw something up if another solution does not appear. Search on full wave with google, it ought to give you a reasonable staring point. I think I linked to this earlier in a discussion of the power supply.

Don't get your solder in a knot, we'll get this straightened out.
regards,
Douglas