A 10,000uF/50V electrolytic capacitor completes the filtering of the 28.8V. Yep, C1 is a real clunker. You can use larger if you like, just watch it when you power up. Without a ‘power-up’ delay circuit of sorts it will probably blow-up the 723 if the capacitor (C1) is too-large. The DC voltage coming from BR1 is fed to the collectors of the in “Darlington” connected 2N3055 NPN power transistors. The base drive for the pairs transistors is coming from pin 10 of the uA723 through a 200 ohm current limiting resistor, R1. Link