Diagnostic details below.
![Image](https://photos.smugmug.com/photos/i-J25VWkj/0/307d0824/L/i-J25VWkj-L.jpg)
Comparison to a new power supply (bottom), the top connector second socket (heated bed positive power input) from the left looks darker and wider.
![Image](https://photos.smugmug.com/photos/i-j7N9wGd/0/be015d4d/L/i-j7N9wGd-L.jpg)
The Rambo board positive power input pin shows discoloration not present on any other pin.
![Image](https://photos.smugmug.com/photos/i-d8TjK3S/0/385548bd/L/i-d8TjK3S-L.jpg)
Dismantling the power connector, shows corrosion that I'm guessing is from arcing? The one next to it is the negative power input socket.
![Image](https://photos.smugmug.com/photos/i-LZhXmBH/0/4f6508db/L/i-LZhXmBH-L.jpg)
![Image](https://photos.smugmug.com/photos/i-8bG4XBN/0/3acead67/L/i-8bG4XBN-L.jpg)
Recently the bed stopped heating mid print. I searched the forum but did not see this problem before.
Steps to diagnose
1) Power connector checked for 24V at the terminal screws on the power connector - Verified to be receiving 24V
2) Replaced bed thermistor with known good thermistor. Both new and old read similar 80-85 and responded to hand temperature change - No change
3) Replaced heated bed with known good heated bed. - No change
4) Replaced Rambo board with known good board - No change
5) Replaced PSU with known good psu - Heated bed successfully heating
6) Replaced old PSU power connector with new power connector - Heated bed successfully heating
I've swapped back in the old heated bed and confirmed that its now heating as expected. My next step is to swap back in the old Rambo board but wanted to check first if that's wise.