This may not be directly related, but I had power indication problems in that the SWR and FWD power readings on my K3 had become erratic with surging of indicated power on CW from a setting of 50W up to 100W and over, yet a constant tune signal was rock steady at 50W. I thought it was an intermittent antenna problem, then switched to it being an SWR measurement problem. I tried everything including two updates of firmware which had temporary benefit but didn't last. Wrote to Elecraft and carried out all checks they recommended except (to my embarrassment) for one which I thought unlikely. There is a lesson here!! Yes, it did turn out to be the real cause and that was to check and tighten the three screws on the bottom cover for the LPA transistors (p63 in assembly manual).
My assumption now is therefore that loose mountings / grounding may have been causing erratic reactive components in the LPA power circuitry leading to sprogs which trigger the much improved VSWR sense circuitry to hunt but never actually find a stable point except when on steady tune up carrier. Incidentally it didn't show up when running low power (10W) using the LPA only. It is so easy to jump to the wrong conclusions; in this case where improvements in the SWR sense loop performance was masking the growing problem with poor ground of key LPA components. After re-reading the Elecraft advice again I did actually check the screws (they were very loose) and tightened them up it all went back to normal. Disconnecting the cables from the K3 to connect to the PC for the firmware uploads must have temporarily disturbed the seating of the LPA screws giving a false and temporary indication of a fix. A regular ragchew contact reported much cleaner rf signal as seen on a pan display after the repair. Dick G3WRJ ______________________________________________________________ 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
