Nothing at all happens without it: what PotEG has to say about the Power Supply
10.7 Power supply poteg-11-7-power-supply 10.7.1 Heating circuit poteg-11-7-1-tube-filament-heater 10.7.2 Filter capacitor poteg-11-7-2-charging-circuit 10.7.3 The internal resistance poteg-11-7-3-impedance 10.7.4 Rectifier tubes poteg-11-7-4-rectifier-tubes 10.7.5 The smoothing filter poteg-11-7-5-filter-chain-capacitors-choke 10.7.6 The mains transformer poteg-11-7-6-mains-power-transformer