[K2] No Transmit Power
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Don:
I am officially stumped. I cannot find the fault in my transmit circuit but that is basically do to my inability to accurately measure ANY RF voltage. The RF probe doesn't seem to function. I have replaced the resistor and resoldered all the connections twice now but I continue to read betwen 50 and 70 mV with any handheld DMM and basically nothing with an HP3478A, I am using the DC volt setting. And all that 50 to 70 mV is across the 4.7Mohm resistor on the probe board. This reading masks almost anything I am trying to measure and without that capability, I am at a loss trying to trouble shoot the transceiver. Connecting the ground lead to the probe still leaves me with the same reading. Is there any other instrument that I can buy or borrow that will accurately measure small RF voltages? Can I buy a working RF probe from Elecraft? Are there only certain DMMs that it will work with? Again, the receiver section and the panel and control functions work just fine but I only get about 0.5 mW on the readout with keydown. Brian Denley http://home.comcast.net/~b.denley/index.html > Brian, >Yes, I am sure about the 4.7 Megohms, but your 4.6 meg resistor will do >just as well. >It is DC voltage through the resistor, and it scales the peak RF voltage >down to approximate RMS. >Look at the schematic for the RF Probe on page 9 of Appendix E in the K2 >manual. >With the RF Probe, you will be able to measure RF voltages down into the >millivolt region. >Go through the steps listed in Appendix E of the manual under Transmit >Signal Tracing. >When you get to the points to measure on page 14 (assuming you do not >find a problem with the VFO or BFO), the RF voltages will be HIGHER than >the expected value because you do not have enough transmit output. What >you are looking for is the first point where the RF voltage is LOWER >than the expected value. That point is just beyond the failing stage, >and you will know which stage to examine in detail. >Only after your K2 is operating properly for RF output will you see the >expected values - go with the higher or lower criteria. >Don ______________________________________________________________ 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 |
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Brian,
Since you are unable to measure any RF voltage, I am going to start at the beginning - proper assembly of the RF Probe. The RF probe voltage is not read "across" the 4.7 meg resistor, it is read between the end of the 4.7 meg resistor and ground. That is an important difference. In other words, the 4.7 megohm resistor is in series with the detector. Since the nominal input resistance of a DMM is 11 megohms (established in the "old days" of VTVMs), that resistance in series with the 11 megohms will cause the DMM to indicate the RMS value of the RF voltage being measured. There are other techniques that will provide DMM readings that indicate the zero to peak RF voltage, but the RF probe parts provided with the K2 will indicate the RMS voltage values when used with most DMMs. The RF Probe parts and board that were provided with your K2 kit should give you the correct connections and RF voltage readings. The TIP should connect to whatever wire you choose to use for the probe tip - I suggest one of the heavy diode leads so it is physically sturdy enough to be pressed onto the point to be measured. The ground wire (with the alligator clip) should connect to the ground symbol point near the tip with a 4 to 6 inch wire and the alligator clip on the far end. The coax should be connected as indicated on the board silkscreen - the shield to ground and the center conductor connects to the end of the 4.7 ohm resistor (follow the PC trace on the board). At the far end of the coax, the red banana plug connects to the center conductor of the coax and the shield connects to the black - you should use a 4 inch length of wire between the shield and the black banana plug. The schematic on page 9 of Appendix E shows "which is connected to what". The banana plugs connect to your DMM, and the DMM will read the RMS value of a sinewave that is probed by the tip (the alligator clip must be connected to one of the ground loops that you should have installed on your K2 RF board). I cannot discern from you postings whether you have things set up correctly to measure RF voltages correctly or not. An oscilloscope can be used in place of the RF Probe, but it must be used with a 10X probe (the voltage readings must be corrected for the 10 times attenuation of the probe), and the "expected" values listed in the manual must be massaged because the 'scope will show you peak to peak voltages which are 2.8 times the RMS values listed in the manual. 73, Don W3FPR On 9/6/2010 10:28 PM, Brian Denley wrote: > Don: > I am officially stumped. I cannot find the fault in my transmit circuit but > that is basically do to my inability to accurately measure ANY RF voltage. > The RF probe doesn't seem to function. I have replaced the resistor and > resoldered all the connections twice now but I continue to read betwen 50 > and 70 mV with any handheld DMM and basically nothing with an HP3478A, I am > using the DC volt setting. And all that 50 to 70 mV is across the 4.7Mohm > resistor on the probe board. This reading masks almost anything I am trying > to measure and without that capability, I am at a loss trying to trouble > shoot the transceiver. Connecting the ground lead to the probe still leaves > me with the same reading. > > Is there any other instrument that I can buy or borrow that will accurately > measure small RF voltages? Can I buy a working RF probe from Elecraft? > Are there only certain DMMs that it will work with? > > Again, the receiver section and the panel and control functions work just > fine but I only get about 0.5 mW on the readout with keydown. > Brian Denley > http://home.comcast.net/~b.denley/index.html > > > Brian, > >> Yes, I am sure about the 4.7 Megohms, but your 4.6 meg resistor will do >> just as well. >> It is DC voltage through the resistor, and it scales the peak RF voltage >> down to approximate RMS. >> Look at the schematic for the RF Probe on page 9 of Appendix E in the K2 >> manual. >> With the RF Probe, you will be able to measure RF voltages down into the >> millivolt region. >> Go through the steps listed in Appendix E of the manual under Transmit >> Signal Tracing. >> When you get to the points to measure on page 14 (assuming you do not >> find a problem with the VFO or BFO), the RF voltages will be HIGHER than >> the expected value because you do not have enough transmit output. What >> you are looking for is the first point where the RF voltage is LOWER >> than the expected value. That point is just beyond the failing stage, >> and you will know which stage to examine in detail. >> Only after your K2 is operating properly for RF output will you see the >> expected values - go with the higher or lower criteria. >> Don > ______________________________________________________________ > 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 > 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 |
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Don:
I brought home a high end 500 MHz Agilent scope from work along with it's 10X probe. It also has a 20 mV per division small signal capability. This should at least allow me to take more accurate measurements (peak to peak) of the transmitter section. More later. thanks again for the help,. Brian Brian Denley http://home.comcast.net/~b.denley/index.html ----- Original Message ----- From: "Don Wilhelm" <[hidden email]> To: "Brian Denley" <[hidden email]> Cc: "Elecraft Reflector" <[hidden email]> Sent: Tuesday, September 07, 2010 12:59 AM Subject: Re: [Elecraft] [K2] No Transmit Power > Brian, > > Since you are unable to measure any RF voltage, I am going to start at the > beginning - proper assembly of the RF Probe. > > The RF probe voltage is not read "across" the 4.7 meg resistor, it is read > between the end of the 4.7 meg resistor and ground. That is an important > difference. In other words, the 4.7 megohm resistor is in series with the > detector. Since the nominal input resistance of a DMM is 11 megohms > (established in the "old days" of VTVMs), that resistance in series with > the 11 megohms will cause the DMM to indicate the RMS value of the RF > voltage being measured. There are other techniques that will provide DMM > readings that indicate the zero to peak RF voltage, but the RF probe parts > provided with the K2 will indicate the RMS voltage values when used with > most DMMs. >>> Signal Tracing. >>> When you get to the points to measure on page 14 (assuming you do not >>> find a problem with the VFO or BFO), the RF voltages will be HIGHER than >>> the expected value because you do not have enough transmit output. What >>> you are looking for is the first point where the RF voltage is LOWER >>> than the expected value. That point is just beyond the failing stage, >>> and you will know which stage to examine in detail. >>> Only after your K2 is operating properly for RF output will you see the >>> expected values - go with the higher or lower criteria. >>> Don >> ______________________________________________________________ >> 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 >> ______________________________________________________________ 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 |
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In reply to this post by Don Wilhelm-4
Don:
I brought home a DSO5054A (very nice 500 MHz Agilent scope!) and I was able to take the better measurements. My measurements were in P-to-P but I have divided them by 2.8 for RMS comparison:\ (all measurments Keydown) 1.) VPWR line (pin 2 of U8 on control board): 5.0 volts this is HIGH 2.) Xmit Mixer Output (pin 4 of U10): 28 mV 3.) Buffer Output (pin 6 of U9): 121 mV 4.) Band-Pass Filter Output (W6): 42 mV 5.) T-R Switch #1 Output (anode of D1): 41 mV 6.) Pre-Driver Output (collector of Q5): 34 mV this seems LOW 7.) Driver Input (base of Q6): 34 mV 8.) Driver Output (collector of Q6): 179 mV this is VERY LOW 9.) PA Inputy (base of Q7): 80 mV this seems HIGH 10.) PA input (base of Q8): 80 mV this seems HIGH 11.) RF Detector Input (anode of D9): 143 mV this is VERY LOW on my own I also measured: 12.) base of Q5: 43 mV 13.) out of C107 43 mV all of the DC voltages in column 1 on page 17 are normal Anything look new? Thanks for any help!! Brian http://home.comcast.net/~b.denley/index.html ----- Original Message ----- From: "Don Wilhelm" <[hidden email]> To: "Brian Denley" <[hidden email]> Cc: "Elecraft Reflector" <[hidden email]> Sent: Tuesday, September 07, 2010 12:59 AM Subject: Re: [Elecraft] [K2] No Transmit Power > Brian, > > Since you are unable to measure any RF voltage, I am going to start at the > beginning - proper assembly of the RF Probe. > > The RF probe voltage is not read "across" the 4.7 meg resistor, it is read > between the end of the 4.7 meg resistor and ground. That is an important > difference. In other words, the 4.7 megohm resistor is in series with the > detector. Since the nominal input resistance of a DMM is 11 megohms > (established in the "old days" of VTVMs), that resistance in series with > the 11 megohms will cause the DMM to indicate the RMS value of the RF > voltage being measured. There are other techniques that will provide DMM > readings that indicate the zero to peak RF voltage, but the RF probe parts > provided with the K2 will indicate the RMS voltage values when used with > most DMMs. ______________________________________________________________ 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 |
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Brian,
VPWR is high because there is not enough output being sensed by the RF detector, and the K2 firmware is telling the control circuit to "add more power". With that fact in mind, there does not seem to be sufficient RF voltage at the Xmit Mixer Output, and the other points beyond it as well - but we will come back to those at a later time if necessary. You are correct that the Pre-driver output is the first point significantly lower than the expected value (and all measurements beyond that add no further value at this time), so the Q5 circuit is the one to investigate. I would suggest temporarily removing T3 to remove the 12 volts from Q7 and Q8 and gives you the ability to safely make measurements without the heat sink installed (Do NOT transmit with the heat sink removed and 12 volts connected to the collectors of Q7 and Q8 - the PA transistors will fry quickly). The first thing would be to make DC measurements at Q5 and compare with the chart in the manual. If nothing looks awry with those measurements, then look at the schematic and find all components in the Q5 stage - examine each one for proper values, good soldering - even to the point of arbitrarily re-flowing the solder with a hot soldering iron (750 deg/F). Add a wee bit of solder during the re-flow process to add some additional flux. If there is a blob of solder on any connections already, wick the excess away and then resolder with a smaller amount. Most new build problems turn out to be soldering problems, followed by toroid lead tinning and by component mis-placement. Those components jump out of their proper holes and get soldered into the wrong places :-) . 73, Don W3FPR On 9/7/2010 10:16 PM, Brian Denley wrote: > Don: > I brought home a DSO5054A (very nice 500 MHz Agilent scope!) and I was able > to take the better measurements. My measurements were in P-to-P but I have > divided them by 2.8 for RMS comparison:\ > (all measurments Keydown) > > 1.) VPWR line (pin 2 of U8 on control board): 5.0 volts this is > HIGH > > 2.) Xmit Mixer Output (pin 4 of U10): 28 mV > > 3.) Buffer Output (pin 6 of U9): 121 mV > > 4.) Band-Pass Filter Output (W6): 42 mV > > 5.) T-R Switch #1 Output (anode of D1): 41 mV > > 6.) Pre-Driver Output (collector of Q5): 34 mV this seems > LOW > 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 |
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?I am just about at the end of my rope trying to get this K2 to transmit.
Nothing is coming out of the transmitter because nothing seems to be going into the PA circuit. The receiver circuits all work fine. All RF board transistors and diodes check out fine as far as DC is concerned but my RF probe does not function and I am unable to find the fault. I suspect the T/R switch or whatever circuit generates the RF signal in the first place but the trouble shooting help in the manual does not go yery deep on those issues. What is my next step? Does Elecraft offer a repair service? I have been at this for 4 weeks now with no progress at all. Thanks Brian Denley http://home.comcast.net/~b.denley/index.html ----- Original Message ----- From: "Don Wilhelm" <[hidden email]> To: "Brian Denley" <[hidden email]> Cc: "Elecraft Reflector" <[hidden email]> Sent: Tuesday, September 07, 2010 11:08 PM Subject: Re: [Elecraft] [K2] No Transmit Power > On 9/7/2010 10:16 PM, Brian Denley wrote: >> Don: >> I brought home a DSO5054A (very nice 500 MHz Agilent scope!) and I was >> able >> to take the better measurements. My measurements were in P-to-P but I >> have >> divided them by 2.8 for RMS comparison:\ >> (all measurments Keydown) >> >> 1.) VPWR line (pin 2 of U8 on control board): 5.0 volts this >> is >> HIGH >> >> 2.) Xmit Mixer Output (pin 4 of U10): 28 mV >> >> 3.) Buffer Output (pin 6 of U9): 121 mV >> >> 4.) Band-Pass Filter Output (W6): 42 mV >> >> 5.) T-R Switch #1 Output (anode of D1): 41 mV >> >> 6.) Pre-Driver Output (collector of Q5): 34 mV this seems >> LOW >>7.) Driver Input (base of Q6): 34 mV >>8.) Driver Output (collector of Q6): 179 mV this is >>VERY LOW >>9.) PA Inputy (base of Q7): 80 mV this >>seems HIGH >>10.) PA input (base of Q8): 80 mV this >>seems HIGH >>11.) RF Detector Input (anode of D9): 143 mV this is VERY >>LOW >>on my own I also measured: >>12.) base of Q5: 43 mV >>13.) out of C107 43 mV >>all of the DC voltages in column 1 on page 17 are normal ______________________________________________________________ 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 |
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?I should add: If I connect a small wire to my K2 antenna and press tune,
it shows a strong signal on any of my receivers at that frequency. So somethings coming out of the K2. Either the ouput signal is low OR the K2 RF detector just doesn't measure it correctly for the ALC circuit. Brian Denley http://home.comcast.net/~b.denley/index.html ----- Original Message ----- From: "Brian Denley" <[hidden email]> To: <[hidden email]> Cc: "Elecraft Reflector" <[hidden email]> Sent: Sunday, September 19, 2010 10:26 PM Subject: Re: [Elecraft] [K2] No Transmit Power > ?I am just about at the end of my rope trying to get this K2 to transmit. > Nothing is coming out of the transmitter because nothing seems to be going > into the PA circuit. The receiver circuits all work fine. All RF board > transistors and diodes check out fine as far as DC is concerned but my RF > probe does not function and I am unable to find the fault. I suspect the > T/R switch or whatever circuit generates the RF signal in the first place > but the trouble shooting help in the manual does not go yery deep on those > issues. What is my next step? Does Elecraft offer a repair service? I > have been at this for 4 weeks now with no progress at all. > Thanks > Brian Denley > http://home.comcast.net/~b.denley/index.html > > > ----- Original Message ----- > From: "Don Wilhelm" <[hidden email]> > To: "Brian Denley" <[hidden email]> > Cc: "Elecraft Reflector" <[hidden email]> > Sent: Tuesday, September 07, 2010 11:08 PM > Subject: Re: [Elecraft] [K2] No Transmit Power > > >> On 9/7/2010 10:16 PM, Brian Denley wrote: >>> Don: >>> I brought home a DSO5054A (very nice 500 MHz Agilent scope!) and I was >>> able >>> to take the better measurements. My measurements were in P-to-P but I >>> have >>> divided them by 2.8 for RMS comparison:\ >>> (all measurments Keydown) >>> >>> 1.) VPWR line (pin 2 of U8 on control board): 5.0 volts >>> this >>> is >>> HIGH >>> >>> 2.) Xmit Mixer Output (pin 4 of U10): 28 mV >>> >>> 3.) Buffer Output (pin 6 of U9): 121 mV >>> >>> 4.) Band-Pass Filter Output (W6): 42 mV >>> >>> 5.) T-R Switch #1 Output (anode of D1): 41 mV >>> >>> 6.) Pre-Driver Output (collector of Q5): 34 mV this >>> seems >>> LOW > >>>7.) Driver Input (base of Q6): 34 mV > >>>8.) Driver Output (collector of Q6): 179 mV this is >>>VERY LOW > >>>9.) PA Inputy (base of Q7): 80 mV >>>this >>>seems HIGH > >>>10.) PA input (base of Q8): 80 mV this >>>seems HIGH > >>>11.) RF Detector Input (anode of D9): 143 mV this is VERY >>>LOW > >>>on my own I also measured: > >>>12.) base of Q5: 43 mV > >>>13.) out of C107 43 mV > >>>all of the DC voltages in column 1 on page 17 are normal > > ______________________________________________________________ > 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 ______________________________________________________________ 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 |
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In reply to this post by bdenley
Brian,
Yes, Elecraft has a repair service. If you contact [hidden email], you should be able to obtain the necessary forms and an RSA number. If they ask you if you have tried contacting support, you can try telling them that you have been working with my suggestions. 73, Don W3FPR On 9/19/2010 10:26 PM, Brian Denley wrote: > ?I am just about at the end of my rope trying to get this K2 to transmit. > Nothing is coming out of the transmitter because nothing seems to be going > into the PA circuit. The receiver circuits all work fine. All RF board > transistors and diodes check out fine as far as DC is concerned but my RF > probe does not function and I am unable to find the fault. I suspect the > T/R switch or whatever circuit generates the RF signal in the first place > but the trouble shooting help in the manual does not go yery deep on those > issues. What is my next step? Does Elecraft offer a repair service? I > have been at this for 4 weeks now with no progress at all. > Thanks > Brian Denley > http://home.comcast.net/~b.denley/index.html > > > ----- Original Message ----- > From: "Don Wilhelm"<[hidden email]> > To: "Brian Denley"<[hidden email]> > Cc: "Elecraft Reflector"<[hidden email]> > Sent: Tuesday, September 07, 2010 11:08 PM > Subject: Re: [Elecraft] [K2] No Transmit Power > > >> On 9/7/2010 10:16 PM, Brian Denley wrote: >>> Don: >>> I brought home a DSO5054A (very nice 500 MHz Agilent scope!) and I was >>> able >>> to take the better measurements. My measurements were in P-to-P but I >>> have >>> divided them by 2.8 for RMS comparison:\ >>> (all measurments Keydown) >>> >>> 1.) VPWR line (pin 2 of U8 on control board): 5.0 volts this >>> is >>> HIGH >>> >>> 2.) Xmit Mixer Output (pin 4 of U10): 28 mV >>> >>> 3.) Buffer Output (pin 6 of U9): 121 mV >>> >>> 4.) Band-Pass Filter Output (W6): 42 mV >>> >>> 5.) T-R Switch #1 Output (anode of D1): 41 mV >>> >>> 6.) Pre-Driver Output (collector of Q5): 34 mV this seems >>> LOW >>> 7.) Driver Input (base of Q6): 34 mV >>> 8.) Driver Output (collector of Q6): 179 mV this is >>> VERY LOW >>> 9.) PA Inputy (base of Q7): 80 mV this >>> seems HIGH >>> 10.) PA input (base of Q8): 80 mV this >>> seems HIGH >>> 11.) RF Detector Input (anode of D9): 143 mV this is VERY >>> LOW >>> on my own I also measured: >>> 12.) base of Q5: 43 mV >>> 13.) out of C107 43 mV >>> all of the DC voltages in column 1 on page 17 are normal > ______________________________________________________________ > 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 > 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 |
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In reply to this post by bdenley
Brian,
DON'T DO THAT! If the K2 is developing any power, it will not do it for long without a 50 ohm dummy load. The PA transistors can go "poof" in a hurry when operated into an open circuit - yes, the small antenna wire is an open circuit. 73, Don W3FPR On 9/19/2010 10:39 PM, Brian Denley wrote: > ?I should add: If I connect a small wire to my K2 antenna and press tune, > it shows a strong signal on any of my receivers at that frequency. So > somethings coming out of the K2. Either the ouput signal is low OR the K2 > RF detector just doesn't measure it correctly for the ALC circuit. > Brian Denley > http://home.comcast.net/~b.denley/index.html > > > ----- Original Message ----- > From: "Brian Denley"<[hidden email]> > To:<[hidden email]> > Cc: "Elecraft Reflector"<[hidden email]> > Sent: Sunday, September 19, 2010 10:26 PM > Subject: Re: [Elecraft] [K2] No Transmit Power > > >> ?I am just about at the end of my rope trying to get this K2 to transmit. >> Nothing is coming out of the transmitter because nothing seems to be going >> into the PA circuit. The receiver circuits all work fine. All RF board >> transistors and diodes check out fine as far as DC is concerned but my RF >> probe does not function and I am unable to find the fault. I suspect the >> T/R switch or whatever circuit generates the RF signal in the first place >> but the trouble shooting help in the manual does not go yery deep on those >> issues. What is my next step? Does Elecraft offer a repair service? I >> have been at this for 4 weeks now with no progress at all. >> Thanks >> Brian Denley >> http://home.comcast.net/~b.denley/index.html >> >> >> ----- Original Message ----- >> From: "Don Wilhelm"<[hidden email]> >> To: "Brian Denley"<[hidden email]> >> Cc: "Elecraft Reflector"<[hidden email]> >> Sent: Tuesday, September 07, 2010 11:08 PM >> Subject: Re: [Elecraft] [K2] No Transmit Power >> >> >>> On 9/7/2010 10:16 PM, Brian Denley wrote: >>>> Don: >>>> I brought home a DSO5054A (very nice 500 MHz Agilent scope!) and I was >>>> able >>>> to take the better measurements. My measurements were in P-to-P but I >>>> have >>>> divided them by 2.8 for RMS comparison:\ >>>> (all measurments Keydown) >>>> >>>> 1.) VPWR line (pin 2 of U8 on control board): 5.0 volts >>>> this >>>> is >>>> HIGH >>>> >>>> 2.) Xmit Mixer Output (pin 4 of U10): 28 mV >>>> >>>> 3.) Buffer Output (pin 6 of U9): 121 mV >>>> >>>> 4.) Band-Pass Filter Output (W6): 42 mV >>>> >>>> 5.) T-R Switch #1 Output (anode of D1): 41 mV >>>> >>>> 6.) Pre-Driver Output (collector of Q5): 34 mV this >>>> seems >>>> LOW >>>> 7.) Driver Input (base of Q6): 34 mV >>>> 8.) Driver Output (collector of Q6): 179 mV this is >>>> VERY LOW >>>> 9.) PA Inputy (base of Q7): 80 mV >>>> this >>>> seems HIGH >>>> 10.) PA input (base of Q8): 80 mV this >>>> seems HIGH >>>> 11.) RF Detector Input (anode of D9): 143 mV this is VERY >>>> LOW >>>> on my own I also measured: >>>> 12.) base of Q5: 43 mV >>>> 13.) out of C107 43 mV >>>> all of the DC voltages in column 1 on page 17 are normal >> ______________________________________________________________ >> 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 > ______________________________________________________________ > 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 > 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 |
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?Don:
I am still trying to get my K2 kit to transmit. Since my last post, I have purchased a power meter and confirmed that virtually no power comes out of the antenna jack when the transceiver is keyed (the meter barely moves on the 20 watt scale). I also purchased a new RF probe kit and so far have the same dismal result: the lowest voltage I can measure (probing nothing) is 380 mV, and also 380mV when I attach the ground clip to the probe tip. Touching my finger to the probe tip gives no result as well. This probe was built with new components from Elecraft, the diode is in the way the silk screen indicates (for the banded end). there is no other way to build it! The only idea I have is to take the probe into work and check it with a nice new Fluke meter with the idea that my 2 multimeters are just not suitable or have the wrong input impedance (needs to be ~10Megohms if I understand the probe circuit). Without some way of measuring RF in the transmitter circuit I am just shooting in the dark. I attempted to check Q24 but it's solder joints are placed right under the small SMT board that is mounted on the backside of the RF board and difficult to reach unless I remove that board. Brian Denley http://home.comcast.net/~b.denley/index.html ----- Original Message ----- From: "Don Wilhelm" <[hidden email]> To: "Brian Denley" <[hidden email]> Sent: Monday, September 20, 2010 6:23 PM Subject: Re: [Elecraft] [K2] No Transmit Power > Brian, > > If there is nothing coming from the internal power detector, you will not > see deflection on the K2 bargraph when keying. > It could be a K2 transmit problem or it can be a problem in the RF > detector. Hard to tell which without further measurements. > > 73, > Don W3FPR ______________________________________________________________ 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 |
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Brian,
Did you use coax for the lead from the RF Probe to your DMM? Behavior like that indicates noise pickup after the detector diode - RF? Magnetic coupling? It is really difficult to say what, you will have to examine your environment as well as your meter. Yes, unless you can get the stray pickup (from whatever source) out of your DMM, you will have a difficult time doing any transmit signal tracing. Hint - take your DMM into work with you and do a 1 to 1 comparison in the same environment with another meter. If there is noise pickup on your meter at home, but not at your work location, having your DMM with you at work will reveal that condition. 73, Don W3FPR On 10/4/2010 10:18 PM, Brian Denley wrote: > ?Don: > I am still trying to get my K2 kit to transmit. Since my last post, I have > purchased a power meter and confirmed that virtually no power comes out of > the antenna jack when the transceiver is keyed (the meter barely moves on > the 20 watt scale). I also purchased a new RF probe kit and so far have the > same dismal result: the lowest voltage I can measure (probing nothing) is > 380 mV, and also 380mV when I attach the ground clip to the probe tip. > Touching my finger to the probe tip gives no result as well. This probe was > built with new components from Elecraft, the diode is in the way the silk > screen indicates (for the banded end). there is no other way to build it! > The only idea I have is to take the probe into work and check it with a nice > new Fluke meter with the idea that my 2 multimeters are just not suitable or > have the wrong input impedance (needs to be ~10Megohms if I understand the > probe circuit). Without some way of measuring RF in the transmitter circuit > I am just shooting in the dark. > > I attempted to check Q24 but it's solder joints are placed right under the > small SMT board that is mounted on the backside of the RF board and > difficult to reach unless I remove that board. > > Brian Denley > http://home.comcast.net/~b.denley/index.html > 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 |
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In reply to this post by bdenley
For getting to Q24 leads, yes the SMT diode gets in the way, but I
have found that most builders have left the leads long enough to bend the board assembly up enough to allow access to the Q24 leads. That may or may not be the case with your construction, but I mention it just in case. Unsoldering one lead to swing it out of the way is not a big deal either. My preference is to unsolder the lead from the RF board (leaving it attached to the small board) - it is easier to re-install the diode that way. 73, Don W3FPR On 10/4/2010 10:18 PM, Brian Denley wrote: > > I attempted to check Q24 but it's solder joints are placed right under the > small SMT board that is mounted on the backside of the RF board and > difficult to reach unless I remove that board. > > Brian Denley > http://home.comcast.net/~b.denley/index.html > ______________________________________________________________ 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 |
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