re: K2 anomaly
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On 29 Nov 2005 at 4:01, [hidden email] wrote:
> IIRC, the most likely cause was that one of the DAC's that monitor the > controls and reports any change was right near a switch point, so very > minor variations on voltages or even just tiny changes in the response > when it is polled for data will sometimes cause it to report an change > in the value by one increment. Of course, the K2 is designed to > display the change whenever something like the power or keyer speed is > changed, so it pops up on the LCD for a moment. I suspect it is also caused by noise on the speed/power pots. The volume pot track is well known to become noisy over time, but the same applies to all four pots. My CW speed pot (K2 2498) is now quite touchy with only a very small change causing a significant change in speed, and the RF gain pot (normally left at the clockwise endstop) is also showing signs of noisiness. Any noise on the speed and power pots will be interpreted by the DACs and cause the transient display change we are all seeing. As others have said, just ignore it. It didn't stop my activity in CQWW with 851 QSOs in the QRP section.. I guess the answer is better quality pots... 73 Dave G3YMC http://www.davesergeant.com _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Dave, G3YMC wrote:
The volume pot track is well known to become noisy over time, but the same applies to all four pots. My CW speed pot (K2 2498) is now quite touchy with only a very small change causing a significant change in speed, and the RF gain pot (normally left at the clockwise endstop) is also showing signs of noisiness. Any noise on the speed and power pots will be interpreted by the DACs and cause the transient display change we are all seeing. --------------------------------------------- In general the audio pots on the K2 don't have a noise problem Dave. The original design of the K2 audio gain circuit put demands on the audio pots they weren't designed for which gave the impression that the pots were going bad in early K2's. Wayne redesigned the circuit and I haven't heard about any problems with noisy controls since. In early K2's, the audio gain control acted as a shunt resistor across a balanced audio line. That required that the pot have essentially zero resistance at minimum. Most pots are not designed to provide that reliably, including the one used in the K2. After a short period of use, the pot would start showing a small amount of resistance near minimum, which made it sound "noisy" and sometimes made it impossible to shut the audio off at minimum. I modified my K2 with Wayne's new circuit four years ago and I've not had a noisy pot problem since. The change was incorporated into the basic K2 some time after the mod was developed because it required changes to the PC boards, so there were a lot of K2's built with the old circuit. I think the change came about around S/N 3000 somewhere. From the comments I've seen, many owners never got around to modifying their units once they had gotten used to the control sounding noisy near minimum volume. If yours hasn't been modified, there are instructions for doing that under "builder's resources" on the Elecraft web site. Look for "K2 AF Pot Application Note". Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Ron D'Eau Claire wrote:
> In general the audio pots on the K2 don't have a noise problem Dave. The > original design of the K2 audio gain circuit put demands on the audio pots > they weren't designed for which gave the impression that the pots were going > bad in early K2's. Wayne redesigned the circuit and I haven't heard about > any problems with noisy controls since. I have to differ. The pots DO get noisy over time; it's just that the original audio pot circuit was especially sensitive to the slightest bit of noise. I didn't make the audio mod for some time because I didn't have the problem. After a while I started to have it, so I made the mod. Now the noise is greatly reduced, but there's still a trace. I will get around to replacing the pot at some point. My RIT control got quite squirrely after a while, and I replaced it. Now it's fine. The new pot I got from Elecraft seemed more substantial (the shaft appears to wobble less) and they may be using better pots now than in my K2 no. 709. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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Vic K2VCO wrote:
> My RIT control got quite squirrely after a while, and I replaced it. > Now it's fine. The new pot I got from Elecraft seemed more > substantial (the shaft appears to wobble less) and they may be using > better pots now than in my K2 no. 709. I also had to replace my RIT pot some time ago... Never had a problem with the audio pot though (original circuit). -- 73, Bob Patten, N4BP Plantation, FL E-Mail: [hidden email] Website: http://www.qsl.net/n4bp QRP ARCI #3412 SOC #1 ARS #799 SMIRK #6625 FISTS #7871 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Vic K2VCO
-----Original Message-----
My RIT control got quite squirrely after a while, and I replaced it. Now it's fine. The new pot I got from Elecraft seemed more substantial (the shaft appears to wobble less) and they may be using better pots now than in my K2 no. 709. -- These comments, and my own experience of the RF gain pot on K2 # 2198 that had some problems until I gave it some contact spray makes me wonder if there is a second source of pots with higher reliability - something similar to the K1's 10-turn plastic tuning pot that some have replaced with a more expensive metal version. Then on the other hand the comment above may imply that this is a non-issue if the quality of the K1/K2 pots really has improved with time. 73 Sverre LA3ZA http://www.qslnet.de/la3za/ _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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