[Elecraft] KIO3B repair

[Joe Subich, W4TV]

> 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.
D1 should do its job.  However, R27 is between the USB cable shield
and circuit common ("ground") which indicates your original failure
was a reverse voltage condition (shield became positive relative to
Vbus).

This does point out the real problem with Elecraft and repair of the
KIO3B ... Elecraft have a ~$400 minimum service fee (@ $100/hr).  A
"simple" repair/replacement of D1/R27 would be more expensive at the
minimum service fee than the replacement KIO3b (when they were
available).  Now, the time to troubleshoot a bad KIO3b might consume
the entire 4 hour minimum if the damage was extensive - although
given my experience with USB products the mast majority of the
problems are likely to be D1 with or without R27 (particularly since
Elecraft seem to have gone to great lengths to isolate the "USB Core"
from "raw" Vusb.

73,

    ... Joe, W4TV


On 2025-05-11 10:40 AM, John Canfield wrote:
> 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
>