[Elecraft] Spurs on 6 meters on FT8 Barney K3LA

[Chester B Scholl Jr]

After further thought at lunch I realize that I did replace both sockets. I still remember getting them unsoldered. My other unrelated comment is that I hope the lessons learned from the K3 will make it into the K4 and that the K4 whenever it appears. Barney K3LA

-----Original Message-----
From: Keith Trinity WE6R [mailto:keith at elecraft.com] 
Sent: Wednesday, June 17, 2020 11:15 AM
To: elecraft at mailman.qth.net; scholl at scholl.org
Subject: Re: [Elecraft] Spurs on 6 meters on FT8 Barney K3LA

Did you re-set the Bias after changing finals and working on the KPA3 and LPA?
1. The 8W vs 12W switch-over point on 6m is normal.
2. If the 6 pins for KPA3 DC power were darkened and you replaced with gold, you *MUST* also replace the corresponding KPAIO3 Riser-Board SOCKET!!
The socket gets cooked internally. Sometimes you can see blueing and heat damage, but not always.
3. Check C28 & C52 capacitors marked "M2" near the Finals output. Some older revs KPA3 they were mounted right between the Final tabs near C50 & C51, they get cracked from thermal cycles and should be replaced and moved out away from the finals and mounted in-between the legs of C50&51. (If cracked, they usually cause spurs on 20m). Elecraft part #
E530321
4. Make sure your WM HP cal number is good, typically 25-55, so the radio is not struggling to make more power than it should, then; I recommend do a manual TX gain Cal at 50W on your main operating frequency because 6m is 4megs wide; IE; "TECH MD" to "on",  TUN PWR" to "nor". Then make note of the number of "TXGN HP", Then set power to 50W exactly, set to your favorite frequency, then long press XMIT to do a TUNE for several seconds. Unkey and check the TXGN HP number. It may or may not change, but should be reasonable, typical numbers are 9 thru 60.
(You can do a 5.0w exactly if you like for the "LP" calibration)
*** Then never, ever, set to 5 or 50w exactly as you may do an inadvertent TX Gain Cal and mess up the numbers.
5. Try the internal 2-tone generator and look at the spectrum using that, maybe you are over-driving with the FT8 audio.
Keith WE6R Elecraft K3 Tech