[Elecraft] KPA3(A) Extender Board for adjusting the output devices bias...?

[Ted G7BQM]

Greetings All,

Having just acquired K3 #00626 to tidy up and use portable but mainly as a transverter driver, I found that the KPA3 Rev B gave no output.  Visual inspection showed nothing amiss.  To start checking it was impossible in the rig except proving that it drew 14 Amps above 12 W for any power demanded.

Took me a while to figure out that as all the odd and even pin pairs are linked, I could use a couple of untwisted pair 20 pin IDC cables with female connectors and double 8mm pin length double male header strips to connect the KPA upside down, outside the back of the rig.  100mm long ribbon cables are sufficient.  This soon revealed some hot smelling electronics so signal tracing at this stage proved to be impossible.

By trial and error removing suspect components for out of circuit testing, D10 pin diode was found to be open circuit.  The KPA3 is currently with the UK dealers for further testing and repair since the D10 MA4P leaded diode appears to be absent from UK stockists and I don’t know if anything else is damaged.

Sorry Charles, I also have not been able to find any referenced information on setting the bias, despite looking for it in case I had to change the power transistors.

73, Ted G7BQM




> On 7 Mar 2019, at 02:47, hawley, charles j jr <c-hawley at illinois.edu> wrote:
> 
> Ok. What are they at the factory?
> 
> Chuck Jack 
> KE9UW
> 
> Sent from my iPhone, cjack 
> 
>> On Mar 6, 2019, at 7:02 PM, Jim Brown <jim at audiosystemsgroup.com> wrote:
>> 
>>> On 3/6/2019 3:11 PM, hawley, charles j jr wrote:
>>> Or again, what are the alignment adjustments for these amplifiers?
>> 
>> There are none. Everything is pre-tuned and tested at the factory.
>> 
>> 73, Jim K9YC
>> 
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