What hazard exists in a power supply immediately after turning it off?

Power supplies use large filter capacitors to smooth out pulsating direct current (DC) into a steady, flat voltage suitable for radio equipment. These capacitors act very much like temporary batteries, storing electrical energy within the circuit. Even after you turn off the power supply and physically unplug it from the wall, these filter capacitors can retain a high-voltage charge for minutes or even hours. If you open the case and touch the internal circuitry, this stored energy can discharge directly through your body, causing a severe or fatal shock. While well-designed power supplies include bleeder resistors to drain this stored charge safely, these resistors can fail. Therefore, you must always treat the internal components as live until you have safely verified the capacitors are discharged. The other options, like circulating currents or leakage flux, dissipate almost instantly when power is removed and do not pose a lingering hazard.