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
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