The prototype is powered by an old Sinclair ZX81 PSU (type UK1200). The types sold for powering electronic keyboards appear to be the most suitable. The unit is powered from an external PSU, since this is cheaper than buying the individual parts! One of the low cost unregulated types with an integral mains plug is suitable, providing it is capable of supplying between 10 and 18 Volts DC at 500mA without too much ripple, the voltage regulator U21 will run cooler if the voltage is nearer the lower end of this range. I have avoided the usual 'Catch 22' situation of requiring a programmed EPROM to make the EPROM programmer work! This design uses readily available components to reduce the likelihood of obsolescence. The EPROM Programmer presented here will program the standard 27 family of devices, from 2716 to 27512, and can be used with any computer which has an RS232 serial port. There has long been a requirement for a cheap straight-forward EPROM Programmer, suitable for occasional home use, without the extra features found on many commercial units.Originally published by Paul Stenning in ETI, January and February 1993
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