First, a few quick "whys": 1) The 7805 is actually a Motorola MC7805CP, date code 7308 with gold leads. Very hard to exactly replace.
2) As per the design of the unit, the 7805 is soldered to the foil side of a single sided, copper clad circuit board with no through hole plating. Lifting the traces seems like a significant possibility that I don't want to risk. 3) I'm still waiting for the components to build the 8 volt power supply. Hopefully they will arrive Monday. 4) No, one thing missing from my bench, that I've never really needed up to now, is a good adjustable DC supply. My have to ask for one for Christmas. Three thoughts have come to me since my original post. 1) I have a 12 volt DC supply. 12 volts seems to be within the VIN range for the 7805s whose data sheets I've now read. Can I simply apply 12 volts? 2) Could I place a resistor in series between the 12V supply and the 7805 to drop the voltage at the 7805 to somewhere around 8? 3) If I was to "tack on" a jumper between VIN and VOUT, would that protect the 7805 and allow me to power the circuit with 5 volts? Thank You, Bill S.
