FYI another update to this. I had the same audio squeal on #4717 and asked Gary AB7MY about it around the same time AB3LS's unit was in for repair. According to Dale K6ZP in Elecraft Service, the fix was:
"The KPA3 that is in for this problem has been fixed. The MMT3904 Q7 used as the 18 Mhz oscillator was turning off and on at ~ 15 khz rate, modulating the 18 Mhz. Replacing Q7 cleared the problem. " Since I had the same problem whenever my unit warmed up, Gary sent me a replacement for Q7. It requires removing the KPA3 module and Q7 is on the underside of the board. Q7 a small SMD transistor but is easy to access. You can replace it yourself if you're familiar with SMD work. I cut the existing device with nippers which made it easy to remove the 3 legs without damaging the PCB pads. After a good warmup calling 3C0E on 10m this morning my PA temp reached ~31C and I no longer have any squeal. BTW mine was always there after it got really warmed up...not just when I transmitted. I never noticed it before AB3LS' comment because I seldom never have my high isolation headphones off, but it would have definitely bothered someone with good hearing if they were using the speaker. 73, Bill W4ZV AB3LS wrote > > I had some questions about this issue mailed to me. > > Here's my update. > > Elecraft sent me a replacement KPA100 and KPA I/O board, of which I > replaced myself. > > The new amplifier and I/O board fixed the problem. No more 12KHz > resonation > coming from the internals of the radio in test, low, and high power modes. > The closest thing I can compare the sound to is the electrical resonation > of a cathode ray tube in a TV, however, it's not as clean. > > Possibly a cold solder joint or bad connection between the amplifier and > I/O board? I don't know. > > 73 > DE AB3LS > > On Fri, Jul 29, 2011 at 4:29 PM, Bill W4ZV <[email protected]> wrote: > >> >> AB3LS wrote: >> > >> > No go. >> > >> > Hooked the radio up to a gel cel battery and we're still getting the >> 12Khz >> > junk coming from something and the clicking between TX and RX. >> > >> > I made a longer recording of the 'junk' and posted it. Cycled between >> TX >> > and >> > RX a few times using the manual TX button on the front. Then finished >> off >> > with a few dits and dahs. All while in TX Test mode. >> > >> > >> http://alien.liltechdude.com/files/index.php?dir=Recordings/&file=kpa3squealrev2.mp3 >> > >> > Anyone from Elecraft have anything on this? >> > >> >> FYI I noticed the same on my #4717 kit (delivered last September). I >> normally use headphones so I never noticed it before. I believe ~12 kHz >> was >> getting into the DSP chain before the LPF mod to the DSP board was done >> so >> perhaps that's a clue. BTW I have no switching PS anywhere and this is >> definitely coming from the K3 itself. >> >> This would be VERY annoying to someone with good hearing in a quiet >> shack. >> I can minimize it by slight head movement (standing waves) but that's not >> a >> good solution. >> >> 73, Bill >> >> >> -- >> View this message in context: >> http://elecraft.365791.n2.nabble.com/K3-KPA100-Squeal-tp6518460p6634869.html >> Sent from the Elecraft mailing list archive at Nabble.com. >> ______________________________________________________________ >> 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 >> > ______________________________________________________________ > 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 > -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-KPA100-Squeal-tp6518460p7358514.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ 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
