It was 'my turn in the barrel' last night. My FT-5 happily finished the last of four 4 hour prints, parked itself, shut down the part fan, heat bed and hot end, and then promptly went poof! I posted over on FB but that will disappear by this evening.
Upon inspection, the only part destroyed that I can see is the MOV on the input. That little fella takes a beating evidently. It just crumbled when I went to move it away from the cross line capacitor block to which it was melted....
I've ordered another PS plus some Chinese MOV'S that will eventually show up. Then I'll see if I can resurrect this one and , perhaps, use it to power just the heated bed.
I upgraded my heated bed a while back to the FT black bed. It came with a 4 amp fuse to replace the 3 amp one in the switch block; however, as you will notice in the photo, the PS has an internal 3 amp fuse so how much protecting the 4 amp fuse does is in question.
The MOV is there, I believe, to protect the supply from in-rush current and spikes in the voltage as it charges the capacitors. It dissipates this excess as heat so, over time, I'm guessing they just get brittle and fall apart as this one did.
I thought someone might find the pictures useful in the future so this is the place to park them.