Thank you Ryan. I took one from an extra Arduino Uno I had and put it on the Mega. All is well!
I’ll order extras next time I get some stuff from you.
I’m figuring I can hack a car phone charger’s guts into the 12v input (on the other side of the green plug) and run my RasPi from the resulting 5V output.
This is all unnecessary really, but I can’t help it….It’s who I am.