Was there a serial # that included the current limiting? Sent from my iPhone
On Aug 28, 2012, at 1:18 PM, "Wayne Burdick" <n...@elecraft.com> wrote: > Dave, > > Do you have the AF amp current-limiting mod in place? The parts for > this mod are installed on the RF board. They've been in production for > quite some time, and we can send them to you on request. > > With the limiter installed, we've seen near-zero problems with the AF > amp IC. > > 73, > Wayne > N6KR > > > > On Aug 28, 2012, at 10:25 AM, Dave Hachadorian wrote: > >> I have blown the speaker amp twice, in two different radios, by >> using a speaker with AGC OFF. POOF! Gone before you can react by >> turning down the audio. >> >> The factory guys report that they have been unable to duplicate >> the problem. Unless you are an EXPERT solderer, replacing the >> speaker amp chip is best done by the factory. The job will run >> about $125 with shipping, maybe a little less if you ship only >> the DSP Board. I don't use the speaker amp any more. I still >> think there is a transient susceptibility problem in that >> circuitry that they have been unable to find. >> >> >> Dave Hachadorian, K6LL >> Big Bear Lake, California >> >> >> >> >> >> >> -----Original Message----- >> From: Mike Goldstein >> Sent: Tuesday, August 28, 2012 9:07 AM >> To: elecraft@mailman.qth.net >> Subject: [Elecraft] K3 speaker audio gone! >> >> I've lost audio from both the internal speaker in the >> K3, >> and from the SPKRS output jack on the rear panel. >> >> At the end of the the first week of using a new NESCAF >> audio >> filter (which drives my speaker) with the K3, I changed bands, >> listened briefly on CW, with the NESCAF filter in the circuit. I >> then changed to SSB, and because the NESCAF filter was adjusted >> for a >> very narrow audio bandwidth, I decided to switch it out of the >> circuit, while the K3 was delivering audio, at a comfortable >> listening level.. >> >> The audio filter was driven from the SPKRS jack on the >> back >> of the K3, using a stereo plug, with one channel floating. The >> SPKRS >> jack was CONFIGured as SPKRS = 1. >> >> A front panel toggle switch on the filter panel turns off the >> power >> to the NESCAF filter, and re-routes the speaker audio connection >> from >> the filter output, to the K3 output directly. I had done this >> often, >> for the first week of operations. >> >> This time, however, I briefly saw a "HI CURR" indication on the >> front >> panel of the K3, and then my speaker audio vanished. >> >> Unplugging all connections from the rear panel SPKRS jack, and >> the >> front panel PHONES jack, no longer allows the K3's internal >> speaker >> to produce audio. Nothing I tried would result in any audio from >> the >> external speaker, after connecting that speaker to either of the >> phono jacks that were tied to the rear SPKRS jack, through the >> stereo plug. >> >> The INPUT jack on the SCAF filter (to which the K3's SPKRS jack >> was >> connected) passes through an isolating capacitor, then a 27K >> resistor, before being connected to the chip in the audio filter. >> >> Resetting SPRKS = 2, in the CONFIG menu, had no effect on >> producing >> audio in the external, or internal speaker. >> >> I still have audio at the PHONES jack on the front panel, so I >> can >> still use the K3. It subsequently accounted for 380 QSOs in the >> NAQP >> CW contest, providing it usual flawless performance. >> >> I still have audio at the PHONES jack on the rear panel, as well. >> >> My theory (and Gary at Elecraft Service agrees it might be the >> cause) >> is that the audio chip in the K3 didn't like the abrupt change of >> load impedance, from 27K (approx.) to infinity, to 8 ohms, while >> it >> was delivering audio.. >> >> I've since soldered a 15K resistor across the input jack of the >> audio >> filter, and will do likewise for any other audio filters I >> encounter, and use. >> >> Puzzling, huh? 73 de VE3GFN >> ______________________________________________________________ >> 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 >> >> ______________________________________________________________ >> 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 > > ______________________________________________________________ > 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 ______________________________________________________________ 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
