I don"t know much about electronics but is 74HC125 chip a 4 in 1 fast switches? I don’t know its purpose or why it was used in design.
Anyways, looking at schematic and datasheet I see An are Inputs, Yn are Outputs and Cn are On/Off pins. When Cn is grounded, then connection is made from An to Yn.
If this is true, than A8, Y9 and C9 are of interest. The other 2 sets used for unknown connector? And 1 set is Xed, possibly not used at all?
I am nor sure about all this so need experts to help.
If it was me. What I would do is carefully lift pins 8, 9, and 10th.
Feel U9 if it still get hot. If still hot. Then lift pins Sets for TX and RX . Again feel if its hot. Then if its still hot, then last set is shorted to or the whole U9 is damaged which you have to replace anyways. Now I would remove U9 and do the Will it Blend test.
Once removed, then test pad 9 for signal like I showed before.
However if removing first set removes the short perhaps you can salvage U9 by re routing to unused set of pins.
Again I speak from limited knowledge so please run it by another person at least.
I wish you best and keep us informed.
Thx.
