[Elecraft] K3: Added protection for RS-232 port

[Nand Kishore]

Hi Don,
            I had a failure of RS 232 port in my K3 # 282.Had to change KIO3
board.
>From reporting the defect to change of board took one week.For me,whatever
defect I encounter in my K3,shipping the whole rig to US is not an option.
I was given an option of changing U1 but I did not 'cos the cost of failure
in
terms of down time was unaffordable.So,I opted to change the whole board.
You know the price of the board,shipping was 80$. I have qty.2 chips( U1 )
on hand which will be used to attempt salvage of KIO3 board for spare.
                  So,I wish this board could be made more robust.

Re: WRTC K3's--any defect analysis?

                     73 de Nandu
                               VU2NKS