Don, I set the K2 up this weekend to try to reproduce this problem. Once again I opened it up and re-installed the K60XV board. I put a scope probe on P1 pin 6.
I did not see the AGC failure mode right away, but I did find an intermittent oscillation on pin 6 at about 15 MHz. It would come and go, but no AGC activation. I removed the board and re-soldered all the components around the LM358. Then I inspected the board and scraped away any residual solder flux in that area of the board between any pins. I also re-soldered the 4.0 MHz resonator, although I did not hear or detect any relay activation when it failed before. After that, I put the board back in with the scope probe and ran it on the workbench for a day. I saw no AGC failure mode and no more 15 MHz oscillation. So, maybe it is fixed? Fingers crossed. > On Nov 28, 2020, at 6:19 PM, Don Wilhelm <[email protected]> wrote: > > Bill, > > It is also a mystery to me that it is intermittent rather than a solid > failure. That might imply that something is breaking into oscillation and > overwhelming the VRFDET line. That is why I suggested you check the > component placement and the diode orientation. > That intermittent condition can also be caused by a soldering problem that > takes some time to appear. > > For the non-transverter bands, it is only necessary that the 4.7pF capacitor > be in the circuit and that relay K1 be in the reset position. > > If you hear a relay click when this problem starts, then look to the firmware > on the K60XV to make sure all its related components are in place - there are > not many. If you do hear the relay click, one thing you can do is to > arbitrarily replace the resonator. While I have never seen an intermittent > resonator (dead one = yes), it is one possibility. > > 73, > Don W3FPR > > On 11/28/2020 5:59 PM, Bill Coleman wrote: >> Thanks, Don, I’ll check it out when I have a chance next week. I appreciate >> your suggestions. At the moment, the K60XV and the K2 are about 35 miles >> apart…. >> >> > Bill Coleman, AA4LR, PP-ASEL Mail: [email protected] Web: http://boringhamradiopart.blogspot.com Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 ______________________________________________________________ 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]
