@dsjstc: Which is why in the various write-ups I have done here, I show in an early step an expample of using a drop of "5-Minute" epoxy on the leads as a strain relief.
Before doing the lead alignment and the soldering.
Notice in this thread there are also links to ways to make the connections without using hot solder.
I am sure you are not the first one to be tripped up by over confidence.
That "na, I don't need to do that" feeling.
And yes, that serial pin out is for a "standard" three lead connector.
(Some of the early K4 devices actually shipped with the connector in-place.)
I have a thread/post with pictures on this forum somewhere about the connectors.