Hi on boot up i had been seeing low voltage as the it scrolled up the screen
then I install raspberry pi op system this came up with a window LOW VOLTAGE
I had built my own power supply 5amp 5.076volts ? for the power cable usb to usb c a china cable was in use / to start with I lifted the voltage to 5.227volts still low voltage / next I cut away the plastic on the usb c male plug it has 4 pads on a circuit board to solder to / which was good as the usb c has 12 contacts top and bottom with pin 6 being +volts Looking at the pads under a magnifying light they are marked +V D+ D- G for -volts / next I took a ex printer cable with thicker multi wire strands and cut the printer plug off / soldered the +volts and 0volts to the correct pads on connecting it to the power supply then through a usb tester (UT658) the result was 5.09v at o.48A / the low voltage has not come up again ...
If you build your own power supply it is necessary to use a big enough PNP transistor to carry the current and of cause a transformer capable of supplying the current If any one is interested may be you can contact me JC33