Hi Heinrich;
Just as Arturo stated one of the issues you had on your circuit is that you needed Open Colector circuits to make it work, additionally, even though you only want to simulate it, you need to set an input for the Diode Bridge, in this case I added a sine wave, 60Hz and 24 V amplitude. Another detail important to mention is that Multisim takes VCC and GND as the default power inputs of your circuits, so if you don't have them on your schematic (you can only place them, even without wiring them) Multism will tell you there is an error. I send you the circuit with a little changes that will help you. If an error appears it will probably be de to your simulation configuration, let Multisim try to fix it and it will probably succeed.
I hope the information is useful
Francisco Arellano
National Instruments Mexico
Field Systems Engineer - Energy Segment
www.ni.com/soporte
