[Elecraft] Power oscillation problem (KPA500+KAT500)

[jerry]

Is the internal autotuner of the TS590S on?

           - Jerry

On 2023-11-21 04:50, Andy Durbin wrote:
> Thanks to those that replied with suggestions.
> 
> This morning I ran some additional testing.  I found I could induce
> the oscillation at 70 W KPA500 output power.  With KPA500 switched to
> STBY I could run 100 W from my TS-590S with no anomalies.  The only
> change in the antenna system configuration is that KPA500 is in STBY
> not OPER.
> 
> The time for onset of oscillation , and the frequency of oscillation,
> both depend on the power level. The higher the power the quicker the
> onset and the higher the frequency.  To me that suggests a thermal
> problem rather than voltage induced breakdown.
> 
> The only ferrite in the 40 m antenna system is in the KPA500 LPF and
> the KAT500 tuning inductors.  The KAT500 inductor configuration was
> the same for 100 W STBY and 70 W OPER test.   Those two facts would,
> if taken in isolation,  suggest a problem in the KPA500 40 m LPF.
> However, the LPF seems happy at 500 W with the dummy load.
> 
> I'm finding it hard to find a failure mode that fits all the test data.
> 
> 73,
> Andy, k3wyc
> 
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