It’s only one wire in the cable, and it’s not the wire, but it looks like the pin, or possibly the crimp point on the female pin.
So a few possibilities:
Bad pins. Female pins (sockets) have internal wipers that grip the male pin and there is also the crimp connection. Bad QA on those leads to hotspots in the pin under high current draw. I’d probably go for this explanation, looking at the photos.
Bad electrical layout on the card that means that the bulk of the current goes through this pin. Milliohms on the track traces are enough to cause imbalances. This might be balanced out by having a small-but-still-larger resistance in the (standard) cable, which leads to:
It looks like thicker cabling is soldered and heatshrinked to smaller cabling that actually goes into the pins in the connector. There’s a reason why industrial cable connections aren’t soldered. Possibly a solder connection on another cable has broken and hidden in the hearshrink leaving more current to pass through this one.
Following from this it’s also quite possible that the thicker cable with less resistance , now has less voltage drop across it, and simply allows more current then designed through a connection already at its limit.
It’s quite possible that there are different pins/connector sets for different current draws. This cable might be using the wrong connector with the same physical size but lower current rating. The fact that the cable has been soldered to skinnier wires in the actual connector suggests this, but it’s quite possible that the connector is the right one.
It’s only one wire in the cable, and it’s not the wire, but it looks like the pin, or possibly the crimp point on the female pin.
So a few possibilities:
Bad pins. Female pins (sockets) have internal wipers that grip the male pin and there is also the crimp connection. Bad QA on those leads to hotspots in the pin under high current draw. I’d probably go for this explanation, looking at the photos.
Bad electrical layout on the card that means that the bulk of the current goes through this pin. Milliohms on the track traces are enough to cause imbalances. This might be balanced out by having a small-but-still-larger resistance in the (standard) cable, which leads to:
It looks like thicker cabling is soldered and heatshrinked to smaller cabling that actually goes into the pins in the connector. There’s a reason why industrial cable connections aren’t soldered. Possibly a solder connection on another cable has broken and hidden in the hearshrink leaving more current to pass through this one.
Following from this it’s also quite possible that the thicker cable with less resistance , now has less voltage drop across it, and simply allows more current then designed through a connection already at its limit.
It’s quite possible that there are different pins/connector sets for different current draws. This cable might be using the wrong connector with the same physical size but lower current rating. The fact that the cable has been soldered to skinnier wires in the actual connector suggests this, but it’s quite possible that the connector is the right one.