Twin Famicom disk drive: Head continuously moves no matter what

[ApolloBoy]

Welp, I modified my new Twin Fami to accept a model 1 Genesis PSU and it looks like I've paid the price for it. While playing an FDS game for nearly an hour, the screen started flickering and the disk drive head started moving without being prompted (!). I opened up the system after shutting it off and found that the heat sink for the 2SB941 power transistor got incredibly hot, so it turned out the system was overheating.

Now while the system still works fine (and even loads disks just fine), the disk drive head continues to move on its own and nothing short of disconnecting the drive has fixed it. Even having the system in cartridge mode doesn't do anything. Anyone have any clue?

 

[ApolloBoy]

So after some help from someone on NESdev, I've determined that the FD7201 drive controller inside the disk drive got partially fried when the system was overheating. I was really concerned that the 2C33 got hit but thankfully it seems to be perfectly fine.

 

[ApolloBoy]

Turns out the FD7201 wasn't at fault, I wound up fixing the issue by replacing both the C311C voltage comparator and 4560 op-amp.

 

[cdamm]

thats good news! im glad its back in action!