Re: [Elecraft] [K3] Strange Selective Hearing in My K3
Sounds like a thermal problem, possibly with the 8v regulator. I have a problem with my K3 (S# 4K range). If the rig is cold ~60 F the 8v apparently goes out of regulation evidenced by the display illumination dimming on key down. The rig works normally otherwise. The problem goes away once the FP Temp warms a little - I wrote the number down somewhere but can’t find it now. Good luck & 73, Brian, K0DTJ > On Oct 10, 2022, at 09:49, Michael Carter wrote: > > Hi Eric, > > I'm voting with my friend Dave, K1WHS, > for looking first at the voltage regulators. > > The 8 volt regulator supplies the TC4427 > gate driver IC, which in turn provides 7R/7T voltages > separately to the Transmit and Receive switching circuits. > The loss of the 7R/7T voltages would disable the > PIN diode T/R switches and render the radio deaf > and unable to transmit. > > If the 8 volt regulator doesn't collapse after some > time observing its output voltage, I would check > the TC4427 (U11 on the RF Board) to be sure its > outputs are correct (the 7R/7T voltages). The > regulator is likely the first culprit - its '8A' output > pin provides power to a large number of circuits > in the radio. > > 73, > Mike, K8CN > __ > 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 > Message delivered to huntin...@coastside.net __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] [K3] Strange Selective Hearing in My K3
Hi Eric, I'm voting with my friend Dave, K1WHS, for looking first at the voltage regulators. The 8 volt regulator supplies the TC4427 gate driver IC, which in turn provides 7R/7T voltages separately to the Transmit and Receive switching circuits. The loss of the 7R/7T voltages would disable the PIN diode T/R switches and render the radio deaf and unable to transmit. If the 8 volt regulator doesn't collapse after some time observing its output voltage, I would check the TC4427 (U11 on the RF Board) to be sure its outputs are correct (the 7R/7T voltages). The regulator is likely the first culprit - its '8A' output pin provides power to a large number of circuits in the radio. 73, Mike, K8CN __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] [K3] Strange Selective Hearing in My K3
When the signals disappear, can you transmit and see RF output? You might be losing one of the regulated DC voltages from the three terminal regulators mounted on the side wall. If you lose TX as well, check to make sure those regulators are working. It will affect all bands. Dave K1WHS On 10/9/2022 5:23 PM, Eric Fitzgerald wrote: I supposed in any lengthy marriage a selective ear or a biological mute button, so to speak, becomes inevitable ...or so it would appear with my aging K3, purchased in 2009. Here are the rather perplexing symptoms: After the K3 has been on a while all signals and noise disappear. The radios shows consistent s1 or 2 white noise. This is true on all bands, all modes and with the preamp, agc, noiseblanker, etc on or off. After turning the radio off for an hour or more, all signals return as normal - only to disappear again after an indeterminate period of time. I'm guessing that there is some failure that is affected by the component in question heating up. I use this radio in receive almost 24/7 monitoring the bands. Perhaps she is just tired of listening for me? ;-) Any ideas what this might be? Stupid operator error is never out of the question around here. I thought I would ask in here before bugging Elecraft service in case I'm missing something easy. TIA Eric KG6MZS www.kg6mzs.com I should add that when I transmit a tone from WJST-X, say, the red light comes on the K3, one bar lights up on the K3's RF meter but no power or SWR is registered on my external meter. So that would seem to eliminate anything disconnected from the rear panel connector via an intermittent connection. If that were the case, I would expect to see a "High SWR" reading before the power folded back. Eric __ 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 Message delivered to k1...@metrocast.net __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] [K3] Strange Selective Hearing in My K3
I supposed in any lengthy marriage a selective ear or a biological mute button, so to speak, becomes inevitable ...or so it would appear with my aging K3, purchased in 2009. Here are the rather perplexing symptoms: After the K3 has been on a while all signals and noise disappear. The radios shows consistent s1 or 2 white noise. This is true on all bands, all modes and with the preamp, agc, noiseblanker, etc on or off. After turning the radio off for an hour or more, all signals return as normal - only to disappear again after an indeterminate period of time. I'm guessing that there is some failure that is affected by the component in question heating up. I use this radio in receive almost 24/7 monitoring the bands. Perhaps she is just tired of listening for me? ;-) Any ideas what this might be? Stupid operator error is never out of the question around here. I thought I would ask in here before bugging Elecraft service in case I'm missing something easy. TIA Eric KG6MZS www.kg6mzs.com I should add that when I transmit a tone from WJST-X, say, the red light comes on the K3, one bar lights up on the K3's RF meter but no power or SWR is registered on my external meter. So that would seem to eliminate anything disconnected from the rear panel connector via an intermittent connection. If that were the case, I would expect to see a "High SWR" reading before the power folded back. Eric __ 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 Message delivered to arch...@mail-archive.com
