After printing ABS for a while (most of the time it failed), I thought it was time to add a heated bed to my vertex k8400.
I bought a mk3 alu heated printbed, and I attached it with a self-made power expander to an external 12v PSU.
Then I noticed that the heated bed wouldn’t turn of, so I resoldered the power expander twice, but it didn’t help.
I then noticed that the heat bed LED indicator is always on, I checked it with external LEDs and it turned out that
the heated bed output on the main board is always turned on…
I tried re-uploading the firmware but it didn’t help.
Have you got any solutions?