Hopefully AGC is not being used at all.
73 de Brian/K3KO
On 5/6/2017 23:46 PM, Nr4c wrote:
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
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