Why 18.6 V? i simulated it first without the capacitor and i actually obtained the clipped rectified wave, but it was clipped at 13.4V, i used a load of 576 Ohm and the limiter resistor was 10k, then i put the capacitor and it was oscillating and it remains contant, well oscillating between 13V and 13.4V then i changed the load to 10K and it remains constant at exactly 13.5V, and if i change the limiter to 1K, i have again the little oscillation, but it is not at 18.6V it is at 13.4 V,
why? i've already checked, by the way the zener is 1N5248B