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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
