Good advice from Salty_Peaks. I'll add a little more...
1) It's surely a bad solder joint *somewhere*. The connector is a good place to look but there's several large (heavy) coils around iron donuts (called torroids) that are notorious for breaking their solder connections to the board. They usually have globs of RTV to hold them in place but they're always a good jarring bump away from failing.
If you have old eyes like me, a magnifying glass is your friend.
And no chance it's the power adapter cord/plug is it? Just another possibility.
Good luck!