Do you have a multi meter, If so do some voltage tests
On the Pi test pins T1 & T2.
1, Test with only the the power plugged in, reading
Should be 5v,( The power adapter output )
If voltage is more than 5v this could cause over heating.
2, If voltage ok, plug in externals one at a time , do voltage
tests each time, if voltage steady all ok
If voltage drops down you could have a problem.
Advice don't mess around the board with a soldering iron.
Don't do any shorting out of fuses or components
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong