Full credit goes to Zachary S. for his findings, I am just providing the information as I felt it would be valuable to someone.
A customer recently sent in a Mac 512k analog board that would start to get power but then die. It would repeatedly tick in fact with popping sound. I went through and checked all the diodes, nothing out of the ordinary. There was one backwards cap, but it was on the horizontal circuit so likely wasn’t “the” issue. Removed the cap, same issue persisted.
I put the board aside for a bit, then someone posted on a Facebook group that they had managed to repair their Mac 512k / Plus analog board. Here is a link to their video on the topic, I don’t want to take away anything from them and they deserve full credit for their findings, link.
Following their video, I checked the blue wire on the cable with the ferrite bead. Looking at the bead, you will see a “5A” and a line. This indicates there’s a fuse in the cable. Checking the blue wire…no beep. I think we might have found it! At the time of this post I have no tested the board but wanted to get this information to the world.