[Elecraft] K2 - KPA100 RS232 interface repair

[K8AC]

Hi Jim.  Well, when this incident occurred, I was deep into working on 
an associated software problem and needed to quickly try the PC serial 
port directly.  I agree with you comment about reading the manual and in 
fact I did so just a couple of weeks back when I acquired this unit.  
Unfortunately, at my age, I don't always recall 100% of what I read.  
Now that I have this problem, of course I remember reading all about 
needing the special cable

But, I disagree regarding the use of the DB9 connector on the K2. Having 
worked on tons of gear with communications ports, I've never run into 
one that purportedly used an RS232 interface, but would self-destruct if 
a real RS232 interface were attached.  The KPA-100 manual clearly 
describes it as an RS232 interface and the schematic has it labeled as 
such.  If it doesn't support RS232 voltage levels, then it isn't an 
RS232 interface in my book.  And I know that there are devices that use 
a DB9 connector but are not RS232 compliant, but that isn't the issue here.

In the document that Gary Surrency and Tom Hammond wrote on the subject 
several years ago, they clearly pointed out the need for a more 
prominent label warning of the possible consequences of connecting the 
wrong cable.  Had I seen such a warning, I'd have remembered the reason 
for it and would have avoided the problem. At any rate, the worst result 
should be a failure to communicate and not the destruction of several 
important components in the unit.  Having read many of your writings, I 
doubt that you'd have ever designed something with that sort of risk 
involved.

When I get everything working again, I plan to document in detail what 
fails, how to determine if it had failed and what to do about it.  
Current documentation on that is rather lacking and I'll bet that there 
are scores of K2s out there with the same problem.

73, Floyd - K8AC


On 8/22/2015 7:26 PM, Jim Brown-10 [via Elecraft] wrote:
> Hi Floyd,
>
> I've owned and operated a pair of K2s, both of which I bought used.
> Elecraft makes it very clear that the DB9 connector on the K2 is NOT an
> RS232 interface, that it is not RS232 compliant, and that a standard
> RS232 cable should NOT be used. Rather, the DB9 connector provides both
> serial control AND several control functions.
>
> The DB9 connector is a generic part, and can be used for many things
> besides RS232.  It is also well known that while the RS232 Standard
> defines voltage levels, MANY modern products produce far less than those
> levels.
>
> I've owned a lot of gear in my lifetime, and the first thing I do is
> open the manual, study it, study the wiring of the various connectors,
> study the specs, and study the operating instructions.
>
> 73, Jim K9YC
>
>





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