[Elecraft] Made a DB15 cable to connect K3 + KAT500, but now Amp is disabled

[iain macdonnell - N6ML]

Very interesting. My understanding of the purpose of the key line
interrupter was to prevent the keying path through the AUX cabling
from reaching the KPA500 when a separate RCA cable path is used which
passes through some external device that also wants to interrupt
keying (such as an external power meter with am protection). If the
AUX pin 10 was left connected, the amp would still be keyed through
that path even if the external device breaks the RCA path.

There must be something more active than relay poles connected to pin
10 in the KAT500 for it to affect the K3 that way. It seems we don't
have schematics for the KAT500, so can only guess........

73,

    ~iain / N6ML



On Thu, Aug 29, 2013 at 7:24 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
> Iain,
>
> Your logic is impeccable, but somehow the KAT500 senses the connection of
> the K3 KeyoutLP signal through the cable pin 10 and attempts to use that
> signal (and ignors the RCA cable PTT).  I do not have the details, but this
> has been reported before - one cannot use both the cable with pin 10
> connected and the RCA cable together.  That is what the Key interrupter
> accomplishes.
> The instructions in the KPA100 manual are correct, (but lack the warning
> that the use of both is to be avoided).
>
> 73,
> Don W3FPR
>
>
> On 8/29/2013 9:43 PM, iain macdonnell - N6ML wrote:
>>
>> It really shouldn't be necessary to remove pin 10 - it should get as
>> far as the relay in the KAT500, and be left dangling there (not
>> connected to anything else). It really shouldn't do any harm. I still
>> think it may be shorted to something else, or there's some other
>> factor at play here that we haven't thought of yet. It would be
>> interesting to see if removing pin 10 does solve the problem, but I'd
>> still wonder why....
>>
>> 73,
>>
>>      ~iain / N6ML
>>
>>
>> On Thu, Aug 29, 2013 at 5:46 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
>>>
>>> Steve,
>>>
>>> Dick's solution will work, but removing the conductor on pin 10 if your
>>> cable is an easier solution.
>>>
>>> What Dick is saying is that you are using both the pin 10 connection and
>>> the
>>> RCA cable PTT connection between the K3 and the KAT500.  I believe your
>>> problem results from attempting to use both.  Since the cable pin 10 will
>>> not activate the RCA cable between the KAT500 and your amplifier,
>>> removing
>>> the pin 10 signal from your cable seems to be the only reasonable
>>> alternative.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>>
>>> On 8/29/2013 6:01 PM, zl2ke wrote:
>>>>
>>>> There seems to be two possible solutions for my amp-disabled problem:
>>>>
>>>> 1.  Remove the wire to pin #10 from my homebrew cable, and still use the
>>>>        RCA cable from the KAT500 to the SB220 amp.
>>>>
>>>> 2.  Make a new cable from the SB220 to the 15 socket on the back of
>>>>        the KAT500 marked "AMP", using pin #10 for the centre conductor
>>>> of
>>>> the
>>>>        RCA cable and pin #5 to the shield/ground of the RCA cable.
>>>>        (Suggested by Dick K6KR.)
>>>>
>>>> Iain, your suggestion of removing the wire to pin #10 is the easiest
>>>> option
>>>> for me,
>>>> but I will wait a bit to see what others say
>>>>
>>>> 73,  Steve   ZL2KE
>>>>
>>>>
>>>>
>>>> --
>>>> View this message in context:
>>>>
>>>> http://elecraft.365791.n2.nabble.com/Made-a-DB15-cable-to-connect-K3-KAT500-but-now-Amp-is-disabled-tp7578367p7578393.html
>>>> Sent from the Elecraft mailing list archive at Nabble.com.
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