Kevin, It is normal to see a higher response touching a random, wire to C6 compared to touching the same wire to W6. The C6 location is a high impedance point while the W6 and D6 locations are low impedance - the capacitive dividers (C7,8 and C4,5) reduce the impedance. The end of a random wire is a high impedance and matches better at C6. If you were connecting the center conductor and ground the shield of a properly matched feedline close to the test point, you would likely find a better response at W6 than at C6. That is why that testing technique is called "Cheap and Dirty" - it does have some eccentricities that the user needs to be aware of (like this one), but overall is a quick troubleshooting aid.
If you are getting about the same response at D6 and W6, then the bandpass filter is probably OK. 73, Don W3FPR Kevin Cozens wrote: > Greetings. > > I have barely used my K2 going on about two years now. It seemed to work > well when I first got it off the person who had assembled it. I got > occasional comments about good audio when operating on SSB. I then > started applying the mods to bring it in line with the post 3000 serial > number units, applied the PLL stability mode, and replaced the crystals > with a more closely matching set, and completely re-aligned the radio. > > Since then, the radio seems to have become slightly deaf, and I also > have some issues with transmit audio. I've considered selling it to > someone who could fix it and starting over. Having acquired a good > digital storage oscilloscope some months back, I'm going to have another > shot at trying to fix the problems. I'll start by working on the receive > issues. > > I'm planning to get one of the Elecraft signal generator kits to help > with tracking down the receiver issues. Since I don't currently have > one, I'm starting with the cheap and dirty signal tracing notes from > Tom, N0SS. I pulled out the KSB2 and disconnected the KAT2 to eliminate > them as a source of problem. I have noticed one odd thing when using a > random length of wire and touching one end of it to the indicated test > points. > > Touching the wire to either side of C6 (RF Board page 3), the S meter > reading on the front panel goes up by about 2 LED's. What is odd is that > if I touch W6, or either end of D6 (the previous and next points in the > signal chain) I don't see this level of increase in signal level. > > This isn't making sense to me right now. I would think I would get the > same signal level increase at either W6, or D6, but not at neither point > compared to both sides of C6. Could this indicate bad, or wrong value > caps, for C5 and/or C7? Any other thoughts about this rather odd > behaviour? Seems to be pointing towards something to investigate further > but I hope I don't have to removed that bottom rear panel as its more of > a pain to remove. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
