[Elecraft] [K2] K2/100 - Serial Port Quit Working

[Matt Maguire]

Don’t forget, you can’t plug in a USB adapter directly into a K2, as the
wiring is not standard RS232C. You need to make up a special adapter as
described in the manual. Probably you know this already, but just something
else to check.

73, Matt VK2RQ

On Fri, 5 Nov 2021 at 06:31, Bill Coleman <aa4lr at arrl.net> wrote:

> About 10 days ago, I was having trouble with the K2/100, as it was no
> longer talking to WSJT-X correctly. I could get the audio running, but it
> would never contact the radio.
> the man eis
> Trying to set up for CQ WW Phone, I had the same trouble with N1MM.
>
> Tried to use the PORT TEST feature by going to the SEC menu, selecting
> PORT, going into EDIT, and pressing the DISPLAY button. It would say TEST,
> but I’d see no characters transmitted.
>
> Since I use USB serial adapters, I tried two of them, to no avail. Can’t
> get a peep out of the K2/100.
>
> Opening up the rig and digging out the scope, if I send characters on the
> serial port, I see pulse trains on KPA100 U4 - the MAX1406 chip - pin 11
> (R3OUT). So, it would appear that characters are reaching the main CPU.
>
> If I put the scope probe on pin 12 (T2IN), it remains locked on ground,
> never moving, even when I do the PORT TEST.
>
> If I remove the P1 connector from the control board, and put the scope
> probe on pin 1 of that connector, I DO see pulse trains from the PORT TEST.
> This indicates to me that the CPU is OK, but something is wrong at the
> MAX1406 chip in the KPA100.
>
> In addition to not getting a response from the K2, it doesn’t appear to
> obey commands. If I send RT1; or XT1; it doesn’t turn RIT or XIT on.
>
> I tried using a different main CPU chip (I have one with older firmware),
> but that doesn’t appear to make a difference. I’m wondering if my problem
> is a blown MAX1406 chip.
>
> Any recommendations or advice? It’s a big pain to remove the KPA100 board,
> so I want to make sure what I’m replacing before I go after it.
>
>
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
> Web: http://boringhamradiopart.blogspot.com
> Quote: "Not within a thousand years will man ever fly!"
>            -- Wilbur Wright, 1901
>
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