== External power supply ==
The official external power modulator provides +20V,-20V DC (err... more probably +20V and 0V) with 500mA (believed to be un-smoothed), from a source of ~220V at 50Hz.
The extenal external power modulator is connected to the computer's internal power modulator, which generates a smoothed 12V and 5V outputs and these provide the power for the IC's.Most or all runs at 5V. The 12V are used for the TV modulator, and for the Expansion Port (and, not sure, maybe elsewhere, too)
The internal power supply is very tolerant and the computer will run with input voltages as low as 6V, but the colours in the palette are weak. If the voltage is increased, the colours become strong, and around 18V-20V, they are all correct. If a low input voltage is used, it is likely that the 12V power output on the expansion connector will not be correct.