Hello all. I have a Sainsmart 4.3" TFT (w/ touch) atop a Mega 2560. I originally had a 5v source going directly to the Mega's Vin/GND pins (through the TFT shield's pins). 5v was achieved by running a 12v source (battery) into a small circuit (see image), which fed directly into Vin and GND pins as stated above. I have since removed those 5v wires from the board, replacing that circuit with a 12v-to-7.5v buck converter from eBay which uses the barrel connector on the Mega instead of the Vin/GND pins.
Ever since then, my sketch does not load when powered solely via the battery (the original 12v source). All I get is a white screen. But then when I attach USB as well, the sketch loads and functions fine. Then if I detach USB while running, the TFT starts to flicker like mad and the sketch becomes unresponsive. Not backlight flickering, think the horizontal lines you get on your TV when you fast-forward your VCR.
In sum, switching power from Vin/GND pins to barrel jack causes my TFT to flicker and not function properly. That's the opposite of what I expected. Obviously I'm wrong, but I thought using the barrel jack smoothed out the power whereas using the Vin pin does not. So what could be causing this issue? Thank you in advance.
