Dom, Yes, that K1 would appear to be deaf - most can hear a -130 dBm signal well above the receiver noise floor. To troubleshoot it, use your oscilloscope (with a 10X probe). First check the crystal oscillator output on each band You can check that at the 2 band board P1 pin 4. You should have at least 200 mV peak to peak on each band. If that test is successful, put the oscilloscope probe on P1 pin 6 and tune the PreMix Bandpass Filters for maximum deflection on the 'scope. Note, that will give you an "almost correct" setting of the inductors, but you will want to peak them during transmit while monitoring the RF output with your scope across the dummy load.
OK, the PreMixer bandpass is adjusted close enough to go on to the next step - this time you will have to be in TUNE. Monitor the 2 band board P2 pin 8 with your scope and adjust the inductors for maximum RF. If the power output goes above 3 or 4 watts, tap the WPM- Button to bring it down - you cannot observe the peak if the power level is anywhere near the maximum because the transmit stages hit their maximum gain, so keep the power output low. If you find output at the antenna in the step above, connect the oscilloscope across the dummy load and re-peak the inductors - you will then be done tuning the bandpass filters - if there is subsequent trouble, have faith in the tuning of those filters and look for another problem. I believe what you will find in the end is a bad solder connection somewhere. If it worked at one time and then stopped working, that is usually an indication of an intermittent solder joint. 73, Don W3FPR Dominic Baines wrote: > Ok this has me a bit stumped... > > First I could get 40m working on RX and TX, but 20m was deaf as a post and no > TX, now it's the other way around. I needed to tweak L7 and L8. > > 40m is band 1 and 20m is band 2. > > Anyone else had this got any ideas? Yes been through 62 and the relays do > switch. > None of L1, L2 L5 and L6 seem to be open circuit. > C's all still C and not shorted (lifted leads, tested and resoldered). > I reset the 40m L completely withdrwaing the cores and then going through > testing with the screwed in with various turns but the signal generator > signals are not detected now. But are on another radio. > I have checked continuity and for solder bridges etc... and the filter board > default without power is band 1. > > Short of sticking the filter board on a VNA as J7 pin 1-8 should be the BPF, > J6 pin 1-7 should be the pre-mix BPF and J8 ping 1 and 8 should be the LPF > (No ATU so J2 bridged). Interested in ideas. > > BTW FT817 will easily pick out a 1uV signal but the K1 cannot seem to manage > anything until about 2.5uV but the spec sheet says 0.15uV which seems > something is wrong is this usual? > How am I measuring the signal: callibrated 50uV signals from xtal oscillator, > step attenuator and an oscilloscope. > > 72 > > Dom > M1KTA > > ______________________________________________________________ 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
