My KPA500 needs less than 20 watts on all bands. Are you just driving it too hard?
Sent from my iPhone ...nr4c. bill > On May 6, 2017, at 3:01 PM, W1GO (Joe) <[email protected]> wrote: > > All, > > One additional factoid of interest … when in ESSB mode, the runaway issue > doesn’t occur; only in standard bandwidth mode. I’ve used standard bandwidth > recently with out the KPA500 on and I’ve had no power out issues of poor > audio reports. Hence, it seems that somewhere after the K3 there are > oscillations resulting (or at least only noticeable) from the narrower > bandwidth signal. Interesting. > > Take care, all. If and when i figure it out I’ll share. BTW, I did switch > miss from a boom with foot pedal to a short cable desk mic just to rule that > out. > > Joe > >> On May 6, 2017, at 12:49 PM, W1GO (Joe) <[email protected]> wrote: >> >> >> 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 t ______________________________________________________________ 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]
