Jason, Visually check the two transistors that form the preamplifier for the frequency counter (Q9 and Q10, I think). If they have a shiny bluish face on the flat side, Elecraft will send you two replacements (totally black). I had this exact problem caused by low or no gain in the transistors. Just a bad lot apparently. See Elecraft Builders Alert #21 of October 19, 2004.
73, Fred K6DGW Auburn CA CM98lw W3FPR - Don Wilhelm wrote: > > Jason, > > Yes, 2456 kHz IS way too low - in fact it is quite out-of -bounds - and is > close to only half the frequency that it should be. > > First thing to check is soldering, then re-check the soldering, and when you > are finished, check soldering again. Use the schematic to identify those > components in the BFO area and check them carefully for good solder joints > and proper values. > > Be certain the varactor diodes are the correct type, and be certain the > crystal the correct one and is properly soldered. The BFO is a VXO type > circuit, and if everything is proper, it would be very difficult if not > impossible to pull a good crystal by 50% of its frequency. If everything > else is correct, you may have a bad crystal (or perhaps it is shorted at the > solder joints by excess solder) - consider removing the crystal, cleaning up > the solder and putting it back in. > > Lastly, look for something wrong with either the counter probe or the RF > voltage at the BFO test point. It is possible (but not probable) that the > voltage is high enough to properly count the frequency at the high end, but > drops off at the low end and counts only approximately half the pulses. If > you have a 'scope (or build the RF probe included with your K2 kit), it > should be able to tell you if the RF voltage is really lower at the low > frequency end. > > The calibration of the 4 MHz reference may cause reading to be off by a bit, > but not nearly the difference you are reporting. If you set it with another > receiver, you are close enough for now - you can refine it later when you > have completed the K2 and are ready to do a precise dial calibration. I > recommend using the most recent method of zeroing WWV and comparing the BFO > and VCO frequencies (previously known as the N6KR method). Details are on > the Elecraft website and can also be found in the K2 dial calibration > article on my website www.qsl.net/w3fpr. > > 73, > Don W3FPR > > ----- Original Message ----- > From: "Jason Marten" <[EMAIL PROTECTED]> > > > I've come to the Alignment and Test, Part II. I think I'm having a > > problem under the BFO test. > > > > Following the instructions, I switch to 40m, hook up the frequency counter > > to TP2, and get a reading of 4913.52. The manual says I should get > > something between 4908 and 4918. So far, so good. > > > > Next, I go to the part where you determine the BFO range. After hitting > > Band+, I get a reading of 4917.54 kHz. The manual says you need >= > > 4916.3, and it's usually between 4916--4917. Maybe a tad high, but looks > > good to me. After hitting Band-, I get a reading of 2456.11 kHz. The > > manual says it must be <= 4912.7 (which it most certainly is) but it is > > usually about 4909--4912 (which is isn't, by a long shot). This results > > in a range of 2461.43. The manual says it must be >= 3.6 (which it is, by > > a lot), but it's typically 4--6 kHz. > > > > It looks like I'm meeting the letter of the law based on the >= and <= > > requirements, but I'm nowhere near the typical ranges on the BFO low freq. > > and range. > > > > Following this test in the manual is some info on what to do if the > > frequencies are too high or too low: > > > > First off, I did not use a frequency counter to adjust C22 on the control > > board, I used a separate receiver and hooked up a wire from its antenna > > jack to the 4 MHz crystal, as described in the manual. This resulted in > > me turning C22 less than 30 degrees counter clock wise (anti clock wise). > > This seems reasonable to me, so I don't think C22 is off by very much. > > However, I think I might want to try using a frequency counter, to get a > > little more accuracy in calibration. Could anybody recommend an > > affordable frequency counter? I've never shopped around for them, so I > > have no clue as to the price, etc. > > > > The third point mentions I might have shorted out part of L33. Looking > > under a loupe, I did not see any evidence of a short, and in fact, I can > > slide L33 underneath R116, it doesn't appear that heating R116 affected > > L33. > > > > The fourth point mentions L33 could be broken. I put my DMM on the tiny > > leads attached to R116 and got 1.7 Ohms. Does this sound reasonable? > > > > The final point says to check the capacitors and diodes in the BFO > > circuit. After another quick look, this appears to be OK to my eyes. > > > > Any help would be appreciated! > > > > > > _______________________________________________ > > Elecraft mailing list > > Post to: [email protected] > > You must be a subscriber to post to the list. > > Subscriber Info (Addr. Change, sub, unsub etc.): > > http://mailman.qth.net/mailman/listinfo/elecraft Help: > > http://mailman.qth.net/subscribers.htm > > Elecraft web page: http://www.elecraft.com > > > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. 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