Thank you for your patience, I had to make the diagram and write the test instructions:
Please test voltages with the board powered on, and check continuity (if short exists) with the board powered off. Please have the SD Card remove from the board entirely.
In this diagram I show:
- Ground (Gnd) with Black Square
- VMOT Rail with Red Square
- 5v with the Green Square. Touch it with the probe from the right so you do not touch any other pin, and be careful not to touch the SD card casing.
- 3.3v with the Orange Squares - either on the SERIAL Header pin #2 from the left, or the head of the AMS1117 component - whichever you can access easier.
With the board powered on, and your multimeter in voltage measurement mode (mine has maximums of 2, 20, 200v and I choose the 200v mode for this) please place and keep the negative probe on Ground.
Place the positive probe on VMOT. You should see a steady 24v.
Place the positive probe on 5v. You should see a steady 5v.
Place the positive probe on 3.3v. You should see a steady 3.3v
For each of those, please tell me what happens.
Now, please power off and disconnect everything from the board.
Set the meter to continuity mode to check for shorts at the same 3 locations:
VMOT - GND
5v - GND
3.3v - GND
If there is a short between any of these 3 rails please let me know.