Picked up a couple of 5711's from our local "surplus" electronics dealer. They appear to do the trick - hasn't glitched once since I switched out the 4148 (914) diodes.
Jim > -----Original Message----- > From: Tom Hammond [mailto:[EMAIL PROTECTED] > Sent: Monday, May 09, 2005 4:15 PM > To: [EMAIL PROTECTED]; 'Jim Sheldon'; elecraft@mailman.qth.net > Subject: RE: [Elecraft] K2: Erratic action of the Hand Key > "Autodetect" function > > > If Sverre's solution to the problem (Schottky diodes) is the > answer, then > the 1N5711 should work nicely... and they are pretty easy to > find... even > if you order them from Elecraft. > > 73, > > Tom N0SS > > At 02:14 PM 5/9/05, Sverre Holm wrote: > >-----Original Message----- > >My K2 (and I've talked with several other K2 owners with the same > >problem), Serial #4338, will not always detect a hand key > properly -- > >Autodetect is turned on in the menu - and I am using 2 1N914 diodes > >between the hand key contacts and the dot and dash inputs to > the K2. > >The keypaddles function properly at all times, but when > using the hand > >key, at random times, a key down on the hand key produces the same > >results as a paddle press - namely automatic dots or dashes. > >---- > > > >I have resolved a similar problem some time ago that > hopefully may shed > >some light on your problem also. The symptom appeared similar, > >seemingly random keying. > > > >The series diodes in the autodetect circuit will make the K2 > input no > >longer 0, but say 0.7 Volts (for Si diodes) when keyed. When > I tried to > >key the K2 using autodetect and the diodes from my PC via an > >optocoupler I got into trouble. The saturation voltage of the > >optocoupler was not small enough and when added to the 0.7 > Volts, the > >total was not low enough for the K2 to reliably sense a key-down. > > > >The optocoupler (4N31) had a voltage of 0.65 to 1.8 V in > saturation. I > >lowered it by increasing the drive current in the LED, but still had > >almost 1.4 V (opto 0.65 + Si diode 0.7). The remedy was to > replace the > >autodetect diodes with Shottky diodes. I have several hundreds of > >PRLL5818 in my shack so I used one of them, but the type is not > >critical at all. The data says Vf < 0.33 V at I = 100 mA, so the > >forward voltage with the low current here is even smaller than that. > > > >73 > > > >Sverre > >LA3ZA > >http://www.qsl.net/la3za/ > > > > > >_______________________________________________ > >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 > _______________________________________________ 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
