[Elecraft] K3: Added protection for RS-232 port

[hb9ari]

Hi Pete,

I will look around U1 on the KIO3A!
Never had an RS232 failure since >30y
and never disconnect them when not in use...
only when connecting an other device...
I always thought it was a "relatively" robust
interface!

Thanks for info!

73 QRO,

Rudolf, HB9ARI (K3 #1212)


Pete Smith wrote:
> Don, I have read several reports on this list of RS-232 failures 
> (probably implicating U1 on the KIO3A) apparently due to induced 
> voltage.  My comment was based more on my having used radios with serial 
> ports for some 15 years and never had any problem with the ports, 
> despite leaving serial cables connected all the time.  Elecraft advised 
> me always to disconnect any cable from the RS-232 port on my K3 when not 
> in use, from which I inferred fragility.
>
> Anyway, the point is that I'm ready to add some protection, if I can 
> figure out how to do it.
>
> 73, Pete N4ZR
>
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>
> On 7/18/2010 10:31 PM, Don Wilhelm wrote:
>   
>> Pete,
>>
>> I am not certain why you believe the K3 RS-232 port to be "fragile".  
>> I have not seen a large number of failures identified on this reflector.
>> There have been quite a number of users who have had problems with USB 
>> to RS-232 adapters, but that is not a failure of the K3 RS-232 port.
>>
>> Can you give me some examples of RS-232 port failures on the K3?
>>
>> 73,
>> Don W3FPR
>>
>> Pete Smith wrote:
>>     
>>> I've been thinking about how one might go about adding some 
>>> protection for the apparently fragile (and expensive) RS-232 port on 
>>> the K3.  It might be possible, if the components were small enough, 
>>> to add them on the KIO3 I/O daughterboard, or perhaps on a little 
>>> external board mounted at the port.
>>>
>>> But the question is, what components?  I have seen small gas tube 
>>> units, but suspect that by the time the potential reaches 90 volts or 
>>> so and the tube flashes over, the RS-232 transceiver is probably 
>>> toast anyway.  Would it be feasible to use fast diodes to shunt the 
>>> data lines to ground at .7 volts or so, or would that introduce other 
>>> problems (stray capacitance, etc.)?  Anything else that might make 
>>> sense?
>>>
>>>       
>>     
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