Hi,
I understand what you mean no buttons now, Some suggestions,
Is this a US or NSW machine? ie a large full size IO board the same as the main board or two smaller boards as well as the main board in the cage?
You changed the power supply and it failed after leaving it on and then turning it off?? Check to make sure you have:
+24v available on pins 10,11,12 and ground on pins 3,4,5 and 7 on P17 of a US backpane
+24v available on pins 4,5,6,7,8 and ground on pins 11,12,13,14and 16 on P29 of a NSW backpane
Did you remove the IO boards from the logic box at all? if so remove the logic board and inspect the pins on the IO connector, especially J1 on the US board.
Its interesting both the buttons and meters are not working. hence why I am thinking power supply 24v connection.
cya