K2/10 Low power
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Serial # 4455
What would cause the following low power after all the bandpass filters have been peaked? maximum power setting 160 meters - pwr= 2 watts 80 mtrs-pwr= 6 watts 40mtrs-pwr= 7 watts 30mtrs-pwr= 8 watts 20meters-pwr=3 watts 17 meters-pwr =2 watts 15 mtrs- pwr= 3 watts 12 mtrs-pwr=1.5 watts 10mtrs-pwr 1.0 watt Byron / N4AX ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Byron,
There is no single cause, other than to say that somewhere in the transmit RF chain there is a problem. Turn to the back of the K2 manual and do the Transmit Signal Tracing procedures. While doing the procedures, work in the order listed. You may ignore RF voltages that are greater than the listed expected value. What you are looking for is the first point where the RF voltage is substantially lower than the expected value. That is the output of the failing stage. Check that stage in detail - component values, solder connections, DC voltages etc. Refer to the schematic to identify the components associated with that stage. 73, Don W3FPR On 1/3/2017 8:46 AM, Byron Allen wrote: > Serial # 4455 > > What would cause the following low power after all the bandpass filters > have been peaked? maximum power setting > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by BYRON
Don,
I have now done more tests and bandpass filter alignments....Don, As you suggested I checked all the voltages in the Elecraft manual on the RF board. All are good... Here is the (MAX) power (OUT) int a dummy load on each band and I noticed something that was peculiar. 10m = 2 watts 12m = 2 watts 15m = 3.5 watts 17m = 4 watts 20m = 5 watts 30m = 10 watts 40m = 12 watts 80m = 12 watts 160m = 4 - 5 watts I notice while on 40 meters that as I decrease the power setting the power out peaks a tiny bit at he 12 oclock position to 13 watts and doesnt start decreasing until I get to 10 oclock and as I turn powerback up after I get past 12 oclock the max power drops off by 1 watt. What do I test or change next? is my driver transistor at fault, just not driving the finals??? Trying to get this resolved before the CQ 160 Meter CW Contest on the 27th, need a true 5 watts during the contest and to not harm my rig during the event. Byron / N4AX On Tue, Jan 3, 2017 at 7:46 AM, Byron Allen <[hidden email]> wrote: > Serial # 4455 > > What would cause the following low power after all the bandpass filters > have been peaked? maximum power setting > > 160 meters - pwr= 2 watts > 80 mtrs-pwr= 6 watts > 40mtrs-pwr= 7 watts > 30mtrs-pwr= 8 watts > 20meters-pwr=3 watts > 17 meters-pwr =2 watts > 15 mtrs- pwr= 3 watts > 12 mtrs-pwr=1.5 watts > 10mtrs-pwr 1.0 watt > > Byron / N4AX > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Byron,
OK on the DC voltages. You may have to resort to measuring the RF voltages as indicated in Appendix E of the manual - Transmit Signal Tracing to find where the failure might be. Check the value of R98 on the bottom of the RF board. The fact that the maximum power drops off significantly on the higher bands tells me that the value of R98 could be greater than the stock value of 270 ohms. What happens to the voltage at RF Board U9 pin 3 when you do a TUNE? It should drop to 1/2 the value that it has during receive. If not, Q20 is not working properly. For your 160 meter problem - is C153 68pF? Also is C68 10pF (if you have an older K2, it may be 4.7pF. On the irregular behavior of the POWER knob, it could be a worn pot - look at the power displayed as you turn the knob - it should be smooth. If it is, my suspicion lies with the value of R98. Remember that the VALC voltage is what actually controls the drive to the TX Mixer, and the value of R98 is a controlling factor in the power control loop damping. If this K2 had the KPA100 installed and the power output went up and down during transmission, the fix is to increase the value of R98 - some builders went too far with the increase resulting in low power on the higher bands and possibly 160 meters. 73, Don W3FPR On 1/19/2017 10:55 AM, Byron Allen wrote: > Don, > > I have now done more tests and bandpass filter alignments....Don, > As you suggested I checked all the voltages in the Elecraft manual on the > RF board. All are good... > > Here is the (MAX) power (OUT) int a dummy load on each band and I noticed > something that was peculiar. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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