VCO Alignment on K2 7109
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All,
I have mad it to page 64. When I check the volts at R30 using my DMM I get 8 volts. I assume that the left side of R30 would be having the front of the radio facing me so the lead I tested was towards adjacent the side panel. It did drop to 7.5v but at that reading the L30 was at what appeared to be it's maximum travel limit toward the top of the can. I searched the reflector and have found that I have 4.0 volts at U6 pin 5. I have 16 turns of red and 4 turns of green wire on T5. When I decrease the frequency from 4000kHz the voltage does drop. Also I bought the toroid's pre wound since my eye sight is not as it used to be. So where should i go from here? 73, Ed KE7HGA |
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Ed,
You seem to have run out of adjustment range on L30. You will have to change the turns spacing on T5 to produce a voltage at R30 that is within range. Since your R30 voltage is 8 volts, when tuned to 4000 kHz, tune to a lower frequency so that the voltage is something less than 8 volts. Once you have done that, alter the spacing on T5 to reduce the voltage even further - adjust until the voltage is at something like 5.5 volts - then adjust L30 to bring it up to 6.00 volts when tuned to 4000 kHz. Once the R30 voltage is set at 4000 kHz, check the ends of each band to be certain the voltage is within range for all bands. If it is not, you may have a capacitor problem in the VFO Range Select area (ask about that problem specifically). 73, Don W3FPR On 6/4/2011 10:09 PM, EMD wrote: > All, > > I have mad it to page 64. When I check the volts at R30 using my DMM I get > 8 volts. I assume that the left side of R30 would be having the front of the > radio facing me so the lead I tested was towards adjacent the side panel. > It did drop to 7.5v but at that reading the L30 was at what appeared to be > it's maximum travel limit toward the top of the can. > > I searched the reflector and have found that I have 4.0 volts at U6 pin 5. > I have 16 turns of red and 4 turns of green wire on T5. When I decrease the > frequency from 4000kHz the voltage does drop. > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Don,
I did as you suggested and now have the voltage set to 6 volts at 4000kHz. I will check each band as well. Thanks for your help! 73, Ed KE7HGA On 6/4/11 10:51 PM, Don Wilhelm-4 [via Elecraft] wrote: Ed, |
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In reply to this post by Don Wilhelm-4
Don,
After setting 80m high freq to 6.0v the low freq 3500kHz measured 1.7V. Everything else measured 8.0v which as you know IS about .5v above the upper limit of the range. I will try to see if I can get some more spacing on the windings on T5 and try again. 73< Ed KE7HGA On 6/4/11 10:51 PM, Don Wilhelm-4 [via Elecraft] wrote: Ed, |
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In reply to this post by Don Wilhelm-4
Don,
My last idea had no effect so it looks like I have a capacitor problem. 73, Ed KE7HGA On 6/4/11 10:51 PM, Don Wilhelm-4 [via Elecraft] wrote: Ed, |
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In reply to this post by Don Wilhelm-4
Hello Don,
I have checked the values of c60 and 61 from L30, as well as c96, c95, c94, c93, c92 and c88 from U6 and they are all correct. D21 and D22 are both V149SL. I don't know if you remember but while I was working on phase 2 I had an issue with a mix varactor diodes but that was in the crystal area and I swapped out the incorrect varactor. 73, Ed KE7HGA |
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Ed,
The fact that your voltage on 80 meters goes from 6 volts to something below 2 volts may indicate a problem with varactors D23 through D26 (the group of 4) - check to be certain they are MV209 and that all are correctly oriented and well soldered. Check the orientation and soldering of D21 and D22. Next check the soldering of relays K13, K14 and K15 - make certain you did not miss soldering pin 1. Then check the values of C71 through C75. Schematic for the RF board sheet 1 shows the VFO range select area, and the Relay Table and VCO Table shown on the K2 Schematic Key page may be required to check the operation of the relays for each band and the capacitors used for each band. Since you have 8 volts at R30 on bands other than 80, make certain you do not have any solder bridges between pins of the relays - be certain C72 is the correct 270 pF value (marked 271). You may have to re-do the 80 meter adjustment of L30 and/or T5 if you change anything. Always check the 80 meter band first and then the other bands. 73, Don W3FPR On 6/5/2011 7:43 AM, EMD wrote: > Hello Don, > > I have checked the values of c60 and 61 from L30, as well as c96, c95, c94, > c93, c92 and c88 from U6 and they are all correct. D21 and D22 are both > V149SL. > > I don't know if you remember but while I was working on phase 2 I had an > issue with a mix varactor diodes but that was in the crystal area and I > swapped out the incorrect varactor. > > 73, > Ed KE7HGA > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/VCO-Alignment-on-K2-7109-tp6441114p6441984.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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