Don, I have checked the below several times. But everything looks fine. And I also checked my DMM with small value of registers. It shows correct measurements. Is it better to RE-solder Q9 for this problem ?
If I have kept this problem on operation, do you think what happen to my K2? So far have no plan to connect an external amplifier. Thank you, Hideki JF1KGX ----- Original Message ----- From: "Don Wilhelm" <w3...@embarqmail.com> To: "JF1KGX" <jf1...@jarl.com> Cc: <d...@w3fpr.com>; <elecraft@mailman.qth.net> Sent: Thursday, July 30, 2009 4:16 AM Subject: Re: [Elecraft] K2/KPA100: External Amplifier Keying Test (PA Key) Problem > Hideki, > > The only other thing that could be wrong is high resistance between the > drain of Q9 and the center of the RCA jack. Check both those places for > good soldering. > > Look at the schematic and you will see the circuit is dead simple. Q9 has > its source connected to ground, and the gate is connected to U1 pin 16 > through R1. The drain of Q9 connects directly to the RCA jack. > There is nothing more to the circuit. > In operation, when U1 pin 16 goes to a high level (5 volts or so), the > voltage at the gate of Q9 is also raised - and will likely be close to 5 > volts. In any case, that should allow Q9 to conduct (with very low > resistance) from the drain to the source. With the source connected to > ground, and the drain connected to the center of the RCA jack, if you do > not have a VERY low resistance between the RCA jack and ground, either > there is a bad solder connection or Q9 is faulty. > > Check your ohmmeter - if it is reading milliohms instead of ohms, the 350 > milliohms would be a normal resistance when TUNE is activated. > > 73, > Don W3FPR > > JF1KGX wrote: >> Don, >> >> I have checked what you advised. >> But envrything looks fine. >> I don't believe that Q9 itself is something wromg. >> >> Thank you, >> Hideki >> JF1KGX >> >> ----- Original Message ----- >> From: "Don Wilhelm" <w3...@embarqmail.com> >> To: "JF1KGX" <jf1...@jarl.com> >> Cc: <elecraft@mailman.qth.net> >> Sent: Wednesday, July 29, 2009 6:47 AM >> Subject: Re: [Elecraft] K2/KPA100: External Amplifier Keying Test (PA >> Key) Problem >> >> >> >>> Hideki, >>> >>> With power off, check the resistance from the source of Q9 to ground. >>> If you can check from the lead of Q9 rather than the solder connection. >>> If it is not zero ohms, you have a soldering problem there. >>> >>> If the source of Q9 is well grounded, next check the voltage at the Q9 >>> gate during TUNE - it should be in the 3 to 5 volt range. - if lower >>> than that, check the soldering and value of R1 and the soldering at U1 >>> pin 16 (pin 16 of U1 should be very near 5 volts during TUNE). >>> >>> If all is good with those checks, Q9 itself is the prime suspect (but I >>> have never hear of one being a problem). >>> >>> 73, >>> Don W3FPR >>> >>> JF1KGX wrote: >>> >>>> Somebody has asked the same before. But nothing has been replied. >>>> Now I have the same problem. >>>> >>>> Page 49 of the KPA100 instructions calls for testing the resistance >>>> between >>>> ground and the tab of Q9 on the KPA100 board (or center conductor of >>>> the PA KEY >>>> output jack, J7). >>>> >>>> According to the instructions, the resistance should drop to less than >>>> 3 ohms >>>> when the K2 is put into TUNE mode. Mine only drops to about 270 ohms. >>>> The >>>> troubleshooting in the KPA100 manual doesn't even include any >>>> information for >>>> what to do if the resistance doesn't drop to less than 3 ohms. >>>> >>>> So far everything else seems to be working correctly with the KPA100. >>>> My serial number is 06617. >>>> >>>> Please advise me. >>>> >>>> Thanks >>>> >>>> Hideki >>>> JF1KGX >>>> >>>> >>>> ______________________________________________________________ >>>> Elecraft mailing list >>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>>> Help: http://mailman.qth.net/mmfaq.htm >>>> Post: mailto:Elecraft@mailman.qth.net >>>> >>>> This list hosted by: http://www.qsl.net >>>> Please help support this email list: http://www.qsl.net/donate.html >>>> ------------------------------------------------------------------------ >>>> >>>> >>>> No virus found in this incoming message. >>>> Checked by AVG - www.avg.com Version: 8.5.392 / Virus Database: >>>> 270.13.34/2268 - Release Date: 07/28/09 06:00:00 >>>> >>>> >>>> >> >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> ------------------------------------------------------------------------ >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com Version: 8.5.392 / Virus Database: >> 270.13.35/2270 - Release Date: 07/29/09 06:12:00 >> >> > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
