I used the continuity tester on my meter and it didn't buzz.
I plugged the controller into my computer and the LEDs lit up. It wouldn't connect in Pronterface at first and gave me:
[ERROR] Could not connect to COM3 at baudrate 250000:
Serial error: could not open port COM3:
[Error 2] The system cannot find the file specified.
I fixed this by reuploading Marlin, after which it connected.
When the PSU was turned on and connected, the PSU continued having the same issue as before. I unhooked it from the controller and it started to run normally as before. I plugged the heat bed directly into the PSU and it started to heat up, so it seems to function, as does the controller.