Elecraft faithful, Any guidance with trouble shooting a KPA500 / K3 issue would be helpful.
Problem: KPA500, primarily in SSB, “redlines” (600W+ LED) after a few seconds of transmission / speech. This seems to be independent of band. With the KPA in standby, the K3 output power holds rock steady as indicated in the KPA. Conditions: - Only about 20W of drive in SSB can result in the “redlining” … To eliminate the redlining, I have to turn drive down to about 18W. … about 20W in CW provides about 500W fairly solid. - The K3 is powered by a 70A supply that does not sag much upon K3 keydown (14V to ~13.7V indicated on K3) - KPA is powered off 240 … I tried two different KPA transformer taps as I noticed with yellow tap the supply voltage right about 60V and occasionally a little below on key down. Supply voltage stays well above 60V with red tap but same “redlining” of the KPA. - Have tried various mic gain compression settings using dynamic mikes. Without amp in-line I do fine with gain 30, compression 20 (10db). I’ve gone as low as gain 15 / compression 15 (~5db) with no impact. - I’ve tried various TXG VCE rating from -1.5 to 1.5 … no impact. - ALC on … ext ALC off …. varied these to see if there would be an impact. None. - SWR (to different antennas) is <1.7 w/o KAT500 and <1.3 w/ KAT500 What I’ve tried / done: - Gain / compression changes as above - Checked K3 supply voltage and no significant voltage drop on key down - Changed power supply to a 35A powering K3 with no change - Varied KPA transformer taps to ensure supply above 60V - Changed coax between K3 and KPA and KPA and KAT500 - Tried with two different antennas / coax runs and had same result - Varied TXG VCE from -1.5 to 1.5 - Performed gain calibration on K3 I’ve had the KPA for about 9 months but primarily operated CW so not sure if this is a recent occurrence. Any other suggestions would be appreciated. Many thanks, all, and have a wonderful weekend. Kindest regards, Joe W1GO ______________________________________________________________ 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]
