[Elecraft] K2 - KPA100 RS232 interface repair

[Don Wilhelm]

Anyone who has purchased a used K2 needs to take notice, lest it happen 
to you too.

That connector is marked AUX I/O for exactly that reason, it is not a 
computer RS-232 connector even though it contains TXD, RXD and signal 
ground.  As a result, one must always use the special cable that is 
built as part of the KPA100 to connect to a computer serial port.

You are not likely to have damaged anything in the KPA100 when 
connecting a standard serial cable to the K2, although KPA100 U6 may 
have a damaged output at pin 6, and the inductors located just behind 
the DE-9 connector should be checked for continuity.
The TXD and RXD signals in the serial cable will connect to U4 just the 
same as if the special cable were used.

You could have also damaged the computer serial port because pin 1 was 
grounded by the K2.

You will find most of the damage will be in the base K2.
Internal signals AUXBUS and VRFDET could have caused the MCU IC to be 
damaged as well as the KSB2.
The fact that the 8R voltage rail appears on that connector, that may 
have caused further damage.

73,
Don W3FPR

On 8/22/2015 1:19 PM, K8AC wrote:
> I had been using an Elecraft USB/serial cable with my recently acquired K2
> and the PC communications worked properly.  In debugging a software problem,
> it was suggested that I try using a real serial port, which I did.
> Unfortunately, I was unaware that I wasn't supposed to use a standard RS232
> cable.  So now, the K2's port won't work with the USB/serial cable either
> and I assume that the interface in the KPA-100 was damaged.  I guess that U4
> (MAX 1406) is a prime suspect for failure in this case.  Any suggestions?
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K2-KPA100-RS232-interface-repair-tp7606571.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to w3fpr at embarqmail.com
>