5v regulator swapped. Two main caps replaced. UHF modulator converted for Lumacode HDMI output. 16k RAM fitted internally. Ferranti ULA replaced with uLA81 chip. Keyboard replaced with Ginger Software microswitch keyboard, which has the legends for the ZXPand+ which gives the ZX81 sound, joystick and SD card functionality. This 40 year old system is set for another forty. After all this, it is only pulling 230mA, which is less than before modification, even with the ZXPand+ on the back!