Re: [Elecraft] [K2] KPA100 Troubleshooting - SWR high on low bands, Loss of power control
On Sep 1, 2012, at 9:02 PM, Don Wilhelm w3...@embarqmail.com wrote: As for your wattmeter problems, I suspect that the diodes D16 and D17 may be half bad. Yes, that is rare, but possible - they have been damaged enough to change their characteristics but not make them either open or shorted. I would recommend arbitrarily replacing them and then try the wattmeter calibration again. For initial settings, adjust R26 to produce 43k ohms to ground as measured at U5 pin 5, and R27 to give 43k ohms as measured at U5 pin 3. After that do the null adjustment and see what happens. Don, Just wanted to report a resolution of my KPA100 problems. I noted earlier that replacing the shorted U6 - EL5146C brought the KPA100 back to life, but the rig was giving me some odd wattmeter and SWR results, especially on 80 and 160m. Replaced D16 and D17 with the proper 1N5711 diodes did the trick. I managed to test one of the diodes I removed (the other was destroyed in the desoldering process), and it showed a nearly correct forward voltage on my DVM, and about 3 times that value when connected in reverse. The diode action of the part was clearly compromised. A new part gave a low forward voltage, and an open when connected in reverse. I suspect these diodes, and possibly the EL5146C might have been damaged by a stray static discharge sometime in the last year. I ordered 10 of these diodes from Mouser. They are only $0.10 apiece, so it makes sense to stock spares. With the new diodes in place, the SWR Null Adjustment went well, giving a clear null down below 100 mV. More importantly, it read an SWR of 1.0 on all bands. The rest of the alignment went smoothly, and the rig appears to be producing the correct power levels on all bands. Made a quick contact with HA8RM on 80m just before writing this message. Thanks for your help! __ 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
Re: [Elecraft] [K2] KPA100 Troubleshooting - SWR high on low bands, Loss of power control
On Sep 1, 2012, at 9:02 PM, Don Wilhelm w3...@embarqmail.com wrote: Bill, I am puzzled why a bad EL5146C would cause an INFO 080 problem. INFO 080 normally is the inability of the MCU to properly communicate with another firmware processor. While it is entirely possible that the EL5146C was dragging down the output of the +5v regulator and causing the KPA100 firmware IC to fault, but I cannot tell from this distance. Don, that was exactly the problem. The EL5146C had shorted internally, and was bringing the 78L05 to current limit at about 1 volt. As for your wattmeter problems, I suspect that the diodes D16 and D17 may be half bad. Yes, that is rare, but possible - they have been damaged enough to change their characteristics but not make them either open or shorted. I would recommend arbitrarily replacing them and then try the wattmeter calibration again. For initial settings, adjust R26 to produce 43k ohms to ground as measured at U5 pin 5, and R27 to give 43k ohms as measured at U5 pin 3. After that do the null adjustment and see what happens. I have some 1N5711's on order from Mouser. Can I substitute plain silicon or germanium diodes as a temporary diagnostic tool? 1N914, 1N4148, 1N270, 1N4001, 1N4007 are some that I have on hand. __ 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
Re: [Elecraft] [K2] KPA100 Troubleshooting - SWR high on low bands, Loss of power control
Bill, Yes, you can substitute 1N4148 diodes - they are not as flat with respect to frequency and the response at very low powers will not be as accurate, but other than that, they will work just fine. 73, Don W3FPR On 9/3/2012 12:51 PM, Bill Coleman wrote: I have some 1N5711's on order from Mouser. Can I substitute plain silicon or germanium diodes as a temporary diagnostic tool? 1N914, 1N4148, 1N270, 1N4001, 1N4007 are some that I have on hand. __ 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] [K2] KPA100 Troubleshooting - SWR high on low bands, Loss of power control
My KPA100 has been giving good service for nine and a half years. Back in July, it was giving me an INFO 080 issue, which I tracked down to a defective U6 - EL5146C on the KPA100. I've successfully replaced this chip, and now the KPA100 is responding. Because of the part replacements, I have gone through the KPA100 alignment steps. The first indication of a problem was during the SWR Bridge Null Adjustment. While I could get a clear null, the display never showed anything less than 1.1 SWR on 40m. Next the Power Calibration. This went fine as well, but when I checked the SWR on all the bands, I received a 1.8 SWR on 80m, and 2.6 on 160m. The highest bands gave a 1.0 indication, but most of the others were 1.1, just like 40m. I double-checked my dummy load with my external watt meter. It appears they are 1.0 on all bands. Doing some full-power tests: * 40m - K2 indicates about 70 watts (7 bars), but the external watt meter shows 100 watts * 80/160m - K2 indicates about 50 watts (5 bars), and sometimes I get a Hi Cur warning. The external watt meter shows 100 watts, or perhaps a little more. Something is obviously wrong with the power measurement circuits here. Any suggestions as to what I should do to troubleshoot this further? __ 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
Re: [Elecraft] [K2] KPA100 Troubleshooting - SWR high on low bands, Loss of power control
Bill, I am puzzled why a bad EL5146C would cause an INFO 080 problem. INFO 080 normally is the inability of the MCU to properly communicate with another firmware processor. While it is entirely possible that the EL5146C was dragging down the output of the +5v regulator and causing the KPA100 firmware IC to fault, but I cannot tell from this distance. As for your wattmeter problems, I suspect that the diodes D16 and D17 may be half bad. Yes, that is rare, but possible - they have been damaged enough to change their characteristics but not make them either open or shorted. I would recommend arbitrarily replacing them and then try the wattmeter calibration again. For initial settings, adjust R26 to produce 43k ohms to ground as measured at U5 pin 5, and R27 to give 43k ohms as measured at U5 pin 3. After that do the null adjustment and see what happens. I just returned from the Shelby, NC hamfest - a good time was had by all even though it was quite hot and humid. 73, Don W3FPR On 9/1/2012 4:31 PM, Bill Coleman wrote: My KPA100 has been giving good service for nine and a half years. Back in July, it was giving me an INFO 080 issue, which I tracked down to a defective U6 - EL5146C on the KPA100. I've successfully replaced this chip, and now the KPA100 is responding. Because of the part replacements, I have gone through the KPA100 alignment steps. The first indication of a problem was during the SWR Bridge Null Adjustment. While I could get a clear null, the display never showed anything less than 1.1 SWR on 40m. Next the Power Calibration. This went fine as well, but when I checked the SWR on all the bands, I received a 1.8 SWR on 80m, and 2.6 on 160m. The highest bands gave a 1.0 indication, but most of the others were 1.1, just like 40m. I double-checked my dummy load with my external watt meter. It appears they are 1.0 on all bands. Doing some full-power tests: * 40m - K2 indicates about 70 watts (7 bars), but the external watt meter shows 100 watts * 80/160m - K2 indicates about 50 watts (5 bars), and sometimes I get a Hi Cur warning. The external watt meter shows 100 watts, or perhaps a little more. Something is obviously wrong with the power measurement circuits here. Any suggestions as to what I should do to troubleshoot this further? __ 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
