[Elecraft] 4 MHz oscillator is too high in frequency (K2)
My aging K2 (#2198) has developed a curious symptom in that the 4 MHz oscillator cannot be adjusted lower than about 4,000,000.55 kHz. It has probably been like this for a while and my BFO settings have probably been done with the incorrect reference. I discovered it by observing that the indicated frequency was about 0.75 kHz off. Questions to the group: 1. Has anybody experienced anything like this, and can it be blamed on aging of e.g. the crystal or on some of the capacitors in the circuit? (BTW I have the KI6WX mod of the oscillator circuit http://mailman.qth.net/pipermail/elecraft/2003-August/022687.html which has worked well before) 2. How can I do a quick fix? e.g. by reinstalling C21=33 pF instead of the 10 pF of the mod above - or some other idea for a fix? 73 Sverre - Sverre, LA3ZA K2 #2198, K3 #3391, LA3ZA Blog: http://la3za.blogspot.com, LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html -- View this message in context: http://elecraft.365791.n2.nabble.com/4-MHz-oscillator-is-too-high-in-frequency-K2-tp7587585.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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] 4 MHz oscillator is too high in frequency (K2)
Sverre Holm (LA3ZA) wrote My aging K2 (#2198) has developed a curious symptom in that the 4 MHz oscillator cannot be adjusted lower than about 4,000,000.55 kHz. This should be 550 Hz too high, that must be 4,000.55 kHz (I think!) - Sverre, LA3ZA K2 #2198, K3 #3391, LA3ZA Blog: http://la3za.blogspot.com, LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html -- View this message in context: http://elecraft.365791.n2.nabble.com/4-MHz-oscillator-is-too-high-in-frequency-K2-tp7587585p7587590.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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] 4 MHz oscillator is too high in frequency (K2)
Sverre, You could add additional capacity across C22 to adjust it into range - you would have to experiment with the value. The range of C22 is likely 6 to 50 pf, so adding 40 pF at a time would retain the C22 bandspread and should allow it to tune. i.e., I would suggest first putting 39 pF in place of the 10 pF - if that does not bring it down far enough, try 68 pF. Of course, the easiest fix is to change C21 back to 33 pF and removing the 10 pF across C22, but you will find the C22 adjustment much more 'touchy'. Even then, you may need some padding across C22. I believe the aging of the crystal is to blame. 73, Don W3FPR On 4/21/2014 10:36 AM, Sverre Holm (LA3ZA) wrote: My aging K2 (#2198) has developed a curious symptom in that the 4 MHz oscillator cannot be adjusted lower than about 4,000,000.55 kHz. It has probably been like this for a while and my BFO settings have probably been done with the incorrect reference. I discovered it by observing that the indicated frequency was about 0.75 kHz off. Questions to the group: 1. Has anybody experienced anything like this, and can it be blamed on aging of e.g. the crystal or on some of the capacitors in the circuit? (BTW I have the KI6WX mod of the oscillator circuit http://mailman.qth.net/pipermail/elecraft/2003-August/022687.html which has worked well before) 2. How can I do a quick fix? e.g. by reinstalling C21=33 pF instead of the 10 pF of the mod above - or some other idea for a fix? __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] 4 MHz oscillator is too high in frequency (K2)
Hi Don, Thanks - heating up the soldering iron now! - Sverre - Sverre, LA3ZA K2 #2198, K3 #3391, LA3ZA Blog: http://la3za.blogspot.com, LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html -- View this message in context: http://elecraft.365791.n2.nabble.com/4-MHz-oscillator-is-too-high-in-frequency-K2-tp7587585p7587598.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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
