Hi all I'm experiencing a funny problem with my K2 s/n 5361. My KSB2 board went through intitial testing without problems, all measured values were OK as per the manual. My TX audio however is horrible. It sounds very choppy (one ham reported to me it sounds 'very restrained'), it seems like the signal is cutting out and then switching back on in a very rapid fashion. I get almost no ALC reading when modulating, neither speaking very closely into the microphone nor a few inches away. At first I thought I was experiencing the well-documented low mike gain problem. When speaking very closely to the microphone (a Kenwood MC43) the audio sounds reasonably clear (distorted but not much gets chopped out) but as soon as I move away from the microphone the chopping effect kicks in. This led me to believe that my mike output level was too low and that the KSB2's noise gate was operating on its gating threshold. I then connected a preamp between the mike and the K2. With the K2 connected to a dummy load I listened to my TX signal through my Kenwood TS570. Varying the preamp gain made no noticeable difference, the audio kept sounding distorted. I then tried the R14 mod (changing the 1k R14 into a 10k resistor). No solution, still very crappy audio (I disconnected my preamp at this stage). At that moment I discovered a funny thing: when speaking into the mike at a distance of approximately 1 foot I noticed that my audio was almost sounding natural. Of course I was not getting any power out of the K2 this way. When I moved the mike closer to my mouth the distortion quickly came back. So, at this moment it looks like I'm grossly overmodulating when I speak at a normal distance from my mike. It sounds a lot better when I speak far away from the mike but then I'm really running QRPp, hi. I've taken the KSB2 board out of the K2 and checked all soldering joints (which seem OK). One of T2's leads looked suspicious so I desoldered T2 and rewound it with the little spare wire I had left and resoldered it. Still no luck. Receive audio is OK so the filters seem do be doing fine.
Any suggestions on where to start looking for the cause of this problem are more than welcome. Thanks in advance Glenn ON4WIX _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
