It was my study. I have not shared it with Elecraft because it seems I am persona non grata with them. Possibly because I manufacture upgrade low voltage/low IMD PA modules for the K3, K3s, and K4. 73, Hal W7YNC
> On 02/15/2026 12:05 PM PST Jon Zaimes, AA1K <[email protected]> wrote: > > > Was this your study Hal? Has it been shared with Elecraft? > > Kind of defeats the purpose of buying a 1500 watt amp if it needs to be run > at lower levels to survive. There are less expensive amps for that. > > 73/Jon > > Jon P. Zaimes, AA1K > Tower climber for hire > http://www.aa1k.us/ > Cell: 302-632-2353 tel:302-632-2353 > > Reviews of AA1K tower work on eham website: > http://www.eham.net/reviews/detail/12922 > > Hug your favorite tower every day, and always stay connected to it. > > > > On Sunday, February 15, 2026, 2:52 PM, dyno lab via Elecraft > <[email protected]> wrote: > > > An independent engineering study has identified internal electrical stress > > conditions within the Elecraft KPA1500 HF power amplifier that occur during > > normal operation at 1500 W output. The analysis, based on oscilloscope > > measurements, spectrum analysis, LTspice modeling, and PCB layout review, > > shows that the PA Output Board experiences elevated drain voltage peaks and > > significant RF ripple on the 50 V supply rail. > > Testing into a 50 Ω dummy load indicated drain voltage peaks exceeding 150 > > V and RF ripple greater than 40 V peak to peak on the supply rail. These > > effects are attributed to an inadequate FET drain choke, insufficient > > center tap bypassing, and inductive PCB traces on the PA Output Board > > layout. > > The high drain voltage peaks far exceed the BLF188 maximum drain voltage > > rating of 135 volts which can cause "Hot Carrier Injection" and FET failure > > under normal operating conditions. And the very high RF ripple on the > > supply rail causes extreme drain voltage distortion resulting in high > > harmonic output and intermodulation distortion. > > The internal stress mechanisms may therefore affect long term device > > reliability when operated continuously at full power. The study recommends > > everyday operation in the 800–1000 W range, with full 1500 W output > > reserved for short SSB bursts. High duty cycle digital modes such as FT8 > > and RTTY are best operated at 600–800 W. > > Test data available upon request. > > Hal > > W7YNC > > > > > On 02/15/2026 9:32 AM PST dlrwild1--- via Elecraft > > > <[email protected] mailto:[email protected]> wrote: > > > > > > > > > Does anyone have knowledge of what is causing 15+ repair returns of the > > > $7K KPA1500 amp? > > > Bob WildermanK3SRO > > > > > > > > > Sent from the all new AOL app for iOS > > > ______________________________________________________________ > > > Elecraft mailing list > > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > > Help: http://mailman.qth.net/mmfaq.htm > > > Post: mailto:[email protected] > > > > > > This list hosted by: http://www.qsl.net > > > Please help support this email list: http://www.qsl.net/donate.html > > > Message delivered to [email protected] mailto:[email protected] > > > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[email protected] > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > Message delivered to [email protected] mailto:[email protected] > > > > > > > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
