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: [email protected] 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:[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
