There are a number of options to power the retro computers described on this website:
A dedicated 5 volt power supply, rated at 1 amp or more, with integral cable and 2.1mm jack plug. Most backplanes include a suitable jack (or “barrel”) socket to connect a 5 volt supply.
A USB ‘wallwort’ 5 volt power supply, rated at 1 amp or more, with a separate USB cable ending in a 2.1mm jack plug. These are often let down by voltage drop along the cable.
Power from the USB to serial adapter, where power is taken from the PC/laptop that is acting as a terminal. This is very convenient, but voltage drop and variations in available current mean this is not guaranteed and will often not work with expanded systems.
A dedicated power supply module with integral voltage regulator.
IMPORTANT WARNING
When selecting a power supply, always check the polarity and voltage. Preferably check with a meter rather than just assume it is working as described. When using a 2.1mm jack plug the centre pin should be positive. Suitable jack plugs will typically be described as 5.5mmx2.1mm or just 2.1mm. Five volt power supplies need to provide between 4.75 and 5.25 volts.
Small Computer Central 