Hello there!
I'm doing the following simple simulation in Proteus:

(1) Voltage source 12V -> (2) LM317-based regulated power supply with ON/OFF switch -> (3) Some 74HC-based schematics

I cannot find a way to connect hidden pins of 74xx ICs (3) to my power supply output (2), so they will power up when I switch my PSU on with a switch during simulation. Now ICs are powered immediately after simulation start by VCC or any other value/rail I define in "power rail configuration", but I need them to be powered with the power my supply outputs during simulation. Is it possible at all? How to shut up internal power in Proteus and use your own power supply rails?
Thanks.

 

double click the chip and click on hidden pin button. You can assign a different net to them.