Nascom News­let­ter

seem unnecessary, but the wrong type setting is likely to destroy the EPROM when the 25 volt supply is switched on by the transistors so be warned!

It helps if the two diodes are of the Shotky variety to keep the volt drop down but the five transistors are not critical provided that they are rated for 25 volts or above and can pass the charging current of 0.1 MFD capacitor required by the 2732.

The 25 volt source is not specified as it may be convenient to find an available stabilised power unit for occasional use. Fig. 3 shows a simple regulator which will accept anything between 26 and 50 volts, giving out 25 volts at up to 30mA continuously. It would be suitable for a well smoothed voltage doubler from one of the transformer windings on the Nascom power supply.

RAM storage is required at locations 0C81 to CC8A inclusive for addresses, byte count and EPROM type.

Fig 3.   Simple Regulator For EPROM Programmer