Used to have the UNO powered (via link on Rev 1 motor shield) from the 12V to motor shield.
Had very strange problems with intermittently having the L293 bridge chip run RED hot (as in Ouch, I burnt my finger type hot!!) , other times all was good.
Found out that the PLUS socket solder contact for M1 was resting on the CASE of the USB connector of the UNO and when the motor turned clockwise with the board properly seated. In reverse, no problem.
Swapped some H Bridge chips etc. and all is good again EXCEPT that whereas before, after writing the program to the UNO via USB, I would disconnect the cable, set the power link on the shield and all would be fine, whereas now the UNO no longer can feed from the shield.
Have tried to suss out the connections but got hopelessly lost.
Anyone have any idea as to what happened and how I might be able to fix it?
All help greatly appreciated.