As Joe suggested, I lowered the 3.3k resistors and now it works great. Thanks for all the input!
73, --Ethan, K8GU/3. On Thu, Sep 6, 2012 at 4:07 PM, Joe Subich, W4TV <[email protected]> wrote: > >> Due to the different impedences between the two it did not work >> (driving one by itself was fine...but not both). I had to add a >> buffer circuit between the ACCY output and the band decoder input. > > The Quadra has 1K series resistors and its inputs are clamped with > diodes to +5V/Ground driving a CMOS buffer/line driver configured > as a switch (input 1/input 2) . The KK1L decoder has 3.3K series > resistors to the opto. > > In all probability the Quadra is "hogging" the available current > from the band data outputs and the PS2501 optos are not getting > enough drive. Replacing the 3K3 Ohm with 1K Ohm input resistors > would probably have been preferable. Even without any loading by > the Quadra, with the K3's 2K2 pull-up and 3K3 current limiting > resistors LED current will be less than 1 mA which is marginal > for a PS2501/4N32 type opto that has a typical current transfer > ratio between 300 and 500% (current gain of only 3 to 5). > > 73, > > ... Joe, W4TV > > > On 9/6/2012 11:07 AM, Greg wrote: >> As Joe mentioned you will need to do the pull up resistor update for >> this to work. >> >> I run a splitter cable off the ACCY port on the K3 with one side going >> to my Quadra amp and the other side to the KK1L board. Due to the >> different impedences between the two it did not work (driving one by >> itself was fine...but not both). I had to add a buffer circuit >> between the ACCY output and the band decoder input. Once I did that >> the KK1L board worked great with the K3 connected to the Quadra at the >> same time. I don't recall what IC I used but it was easy to >> get...think I got it at radio shack. >> If you are only going to be connected to the band decoder you should >> not need the buffer. >> >> 73 >> Greg >> AB7R >> >> >> On 9/6/12, Joe Subich, W4TV <[email protected]> wrote: >>> >>> The PS2501-4 in the inputs of the KK1L band decoder are opto isolators. >>> Pull up resistors will be required in the K3 in order to provide drive >>> to the LEDs in the optos. >>> >>>> My KK1L board (built in 2006) seems to be loading down the K3 band >>>> outputs. >>> >>> The K3 band data outputs are open drain - they can not be "loaded >>> down" as they do not source voltage. Note: the KK1L design uses >>> 3K3 Ohm series resistors to limit current to optos. Depending on >>> the sensitivity (current transfer ratio) of the PS2501-4 you may need >>> to reduce the resistance of those resistors in order obtain enough >>> current through the LED. >>> >>> 73, >>> >>> ... Joe, W4TV >>> >>> >>> On 9/6/2012 12:05 AM, Ethan Miller K8GU wrote: >>>> Is anyone else running a K3 with a KK1L band decoder? The K3 manual >>>> states that "earlier K3s may require external pull-up resistors to 5 >>>> vdc." Did you need to do this? My KK1L board (built in 2006) seems >>>> to be loading down the K3 band outputs. Before I add the pull-up >>>> resistors, I just want to make sure that this isn't a sign of >>>> impending doom... >>>> >>>> Thanks and 73, >>>> >>>> --Ethan, K8GU/3. (K3 S/N 6714, TS-930S S/N 5010245) >>>> >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[email protected] >>> >>> 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:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html -- http://www.k8gu.com/ Repair. Re-use. Re-purpose. Recycle. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
