[Elecraft] KIO3B repair

[John Canfield]

My KIO3B suffered the typical USB failure a few years ago but 
fortunately Elecraft was still repairing the K3s then. They replaced the 
KIO3B board and returned the old one. I kept the old board for a long 
time but got interested in trying to repair the failed board (USB 
defective but RS-232 was fine.)

My USB failure (or I suppose the most obvious one) is on the Digital I/O 
Module (E850646) board. Specifically D1 and R27. D1 is an STMicro 
USBLC6-2P6, an ESD protection device. Mouser part # 511-USBLC6-2P6. R27 
is just a zero ohm resistor, I suppose it's used as a fuse. If it's not 
obvious these are surface mount devices so it does take a bit of 
patience and of course the right tools to replace them (or any surface 
mount device for that matter.)

An intact D1 will have an all black case/housing/shell (whatever you 
want to call it), the defective one on my board literally had the top 
part of the case/shell blown off. R27 is in series with the shield lead 
from the USB connector to ground, my R27 was open. D1 and R27 are 
located very near the USB connector so they are fairly easy to find. D1 
was inexpensive, I forgot how much but I bought five of them just in case.

A caveat, I have not tested the 'repaired' KIO3B board, that's still on 
my to-do list. Hopefully D1/R27 did their jobs and sacrificed themselves 
for the good of the board.

73 John W5TWO (ex WB5THT)
In the Texas Hill Country