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
