[Elecraft] KXPA100 fault issue and low power on 80 and 6m

[Esquer Dave]

Good morning experts,
KXPA100 (serial #996) is back from the Elecraft shop. It spent about 3 weeks unconnected from its KX3. I sent it in because the amp was faulting and shutting down with NO detection of the fault using the KX3 or KXPA100 utilities. The amp relay clicked and … just shut down in both the CW and SSB portions of the bands running ANY power (15watts or higher). My wire antennas are resonant.

The amp came back with a clean bill of health, my faults could not being replicated in the lab. The KXPA100 came back calibrated with factory test equipment (KX3) values. My 90 days of repair warranty is ticking …

The tech suggested that maybe the KX3 was overdriving the amp and suggested I do the Elecraft KXPA100 + KX3 Power Calibration. Beforehand, we eliminating cabling and power supply issues between the 2 units.

I have completed the CAL 75 calibration twice (2 times quickly, as he suggested) and with 110 watts selected on the KX3, the ATU in bypass mode and dummy load connected, I get the following power outputs and SWR readings from the KX3 display. 80 and 6 meters are well underperforming …. So far, I have had no faults, good news! Yes, the dummy load is swept as flat SWR via my RigExpert AA54.

Band	Watts		SWR	TX Gain 
1.840	100			1.6		3.4
3.585	58			1.1		4.6
7.120	87			1.2		4.4
10.130	92			1.3		3.7
14.200	97			1.2		3.0
18.100	98			1.2		2.4
21.200	93			1.2		2.8
24.930	86			1.4		2.4
28.400	93			1.5		3.9
50.125	54			1.1		5.0

For TX Gain (tX.X), see the KX3 manual, Appendix B, page 54. If I put the ATU back in with the dummy load and tune each band, the above values really don’t change at all, even on 80 and 6. The tech mentioned that he was not familiar with the TX Gain values and could not share any light on their goodness or validity. Can anyone speak to their reasonableness?

How do I get 80 and 6 meters to full power from the amp? Am I worrying needlessly? Sorry for the long post, help me, gurus!

Dave, K6WDE, KX3 #4599