The Nascom 1 used a 2708 (1k x 8) UV EPROM. This required a -5V 'bias' voltage in addition to the +5V supply. I managed to fry my 2708 when connecting my home brew PSU by not following the device that the -5V suply must be applied first and removed last when switching the PSU on and off. I solved this by using two separate dual pole switches with the -5V controlled via parallel connected switch contacts and the +5V via series connected contacts avoiding any future accidents.
The Nascom 1 used a 2708 (1k x 8) UV EPROM. This required a -5V 'bias' voltage in addition to the +5V supply. I managed to fry my 2708 when connecting my home brew PSU by not following the device that the -5V suply must be applied first and removed last when switching the PSU on and off. I solved this by using two separate dual pole switches with the -5V controlled via parallel connected switch contacts and the +5V via series connected contacts avoiding any future accidents.
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