?Don: If Owen also has no transmit power on the other bands then are his symptoms identical to mine? Brian Denley http://home.comcast.net/~b.denley/index.html
----- Original Message ----- From: "Don Wilhelm" <[email protected]> To: "Owen B. Mehegan" <[email protected]> Cc: <[email protected]> Sent: Tuesday, October 05, 2010 10:01 AM Subject: Re: [Elecraft] K2: Debugging low transmit power > Owen, > > I am going to assume that you were successful with the Alignmant and > Test Part II and were able to receive 40 meter signals. If not, you > need to backtrack a bit and get receive working first. > > The easiest way to troubleshoot a "lack of power output" problem is to > do Transmit Signal Tracing. You can use an RF Probe or an oscilloscope > with a 10X probe. > > Turn the manual to the Appendix E section titled Transmit Signal Tracing > and begin there. If using an RF Probe, the correct expected values are > listed, but if using an oscilloscope, multiply those values by 2.8 and > observe the peak to peak voltage of the RF waveform. > > An important note - the K2 will normally increase drive in an attempt to > increase the power output if the voltage out of the RF detector is too > small. What that means is that all RF voltages prior to the failing > stage the RF voltages will be higher than the listed expected values. > You will be investigating the transmit chain in the order listed (do not > skip around), searching for the *first* stage where the output is lower > than expected - that is the failing stage which then needs to be > analyzed to determine why it is not operating properly. Measurements > beyond this first failure point are not relevant to that first problem > to be found. > All RF Voltage measurements in the list can be done from the top of the > RF Board. Do not transmit with the heat sink removed. If the PA > transistors do get a bit of drive, will produce output and if the heat > sink is not in place, they will quickly overheat and fry themselves. > > Normal failures are soldering problems, toroid leads or incorrectly > placed components. Active device failures are way down of the list of > failure suspects unless something has caused it to be abused. > > 73, > Don W3FPR > > On 10/5/2010 2:38 AM, Owen B. Mehegan wrote: >> Hello - >> >> Two nights ago I completed the assembly of my K2's RF board, and after >> a visual inspection verification of resistance checks, I assembled the >> radio per the instructions and began the third phase of alignment and >> test. I've discovered a problem right off the bat, though. In the 40 >> meter transmitter alignment section, when I put the K2 into tune mode >> at 2 watts power, I'm only reading .3-.4 watts on the onboard >> wattmeter (it alternates between the two). This is with a connection >> to a 100W dummy load. Varying L1 and L2 has no effect on the power >> reading. >> >> I discovered one mistake: I misread the instructions for winding T4's >> 5-6 and 7-8 windings. I wound these bare wires through BOTH holes in >> the core, in a U shape, thus connecting 6-7 and 5-8 (and very possibly >> all 4 together with a short in the middle - this is what comes of >> staying up too late working on a project!). I corrected this mistake >> tonight, but I'm seeing no change on the measured power. Is it >> possible that this mistake fried something? I never saw any smoke or >> smelled burned silicon, and the thermal pads on Q7 and Q8 look normal. >> >> I have also noticed that if I vary the power adjustment on the front >> panel while in tune mode, I see no change on the wattmeter. That seems >> significant. >> >> These are the other checks I've done so far, per the troubleshooting >> instructions: >> > ______________________________________________________________ > 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
