I ordered eight TO-220 7805ABC regulators from Mouser
electronics. The 0-20 V digital LED panel meter I got didn't have the
needed regulator power supply, so I had to build it. The DPM is for
monitoring a 12 volt battery, and so the input sensing wire to the DPM
also just connects to the same 12v battery voltage that the 5 volt
supply circuit does. Well, I built up a 5V supply on a tiny perf
board, and when I powered up the DPM it would flash random normal
voltages, from around 2 to 12 volts for a brief second and then show
'the overrange indication. So I checked the output of the 7805
regulator, and it's exactly 7 volts, not five. No wonder the DPM isn't
working right. So I tried the other 7805 ICs and get the same exact 7
volts output. How can this possibly be? Its a high end fluke DMM, I am
confident the voltage is not off! I don't think there is even a 7807
regulator, is there? They are indeed marked "7805ABC".