Someone
Experienced Member
The Speccy’s power supply circuit is quite interesting. If I’ve correctly interpreted it comprises of input voltage 9-11V DC (unregulated) to generate +5VDC (regulated) from a linear voltage regulator and its other voltages from a oscillator with some voltage multipliers to get +12VDC, 12VAC and -5VDC (with zener diode). The heat generated from a linear voltage regulator is the excess unused power which is approximately the difference between the input voltage and output voltage multiplied by the current drawn (i.e. power - the higher the input voltage the more heat is dissipated). Usually I’d suggest using an LDO (Low Dropout Out) voltage regulator and a lower input voltage to lower the heat dissipation but in the case of the Speccy other output voltages are reliant upon a minimum input voltage of 9VDC. There are many SMPS replacements for the 7805 coming from brands such as Murata, Traco, Recom, OKI, XP power and others. Just ensure that they meet the specs you need.