OK, now this is starting to make sense. Jim’s K3 has a KIO3, not the newer KIO3B. On the older board, the BAND and PTT lines have pullup resistors to the Vcc rail. When the K3 is powered off, that Vcc rail is at 0 volts, which means the pull-ups are now pulldowns. Thus the K3 is inadvertently keying the KPA500. If the KPA detects that the KEY input is low when the user tries to put it into OPER mode, the amplifier will reject the request and stay in STBY. Thus the condition that Jim is seeing.
Try disconnecting the AUXIO cable from the KPA500 and see if it now operates properly. You may actually need to connect the KAT500 to the KPA using both the AuxIO and phono cables (for PTT) depending on which radio is in use. The main issue is how to disconnect the PTT signal from the K3 to the KPA when using the Icom. Otherwise you may be able to leave the AuxIO cable connected. I know that Fred Cady discussed sharing a KPA between two radios in his book, but has anyone solved this situation - one radio is a K3, the other something else? 73, Jack, W6FB > On Mar 31, 2022, at 9:11 PM, James Bennett via Elecraft > <elecraft@mailman.qth.net> wrote: > > Bob - > > The * appears when I key the K3 and the amp is in operate mode. Likewise if I > key the 705 and the amp is in operate mode, with the K3 powered on. > > If I power off the K3 and place the amp in operate mode WITHOUT KEYING IT, > the * appears, so you are correct - the amp thinks it is being keyed. > > There is a jack on the 705 that allows one to key an external amp. I have > that line running to the amp. Disconnecting it makes no difference the * > appears as soon as I put the amp into operate mode. If I power on the K3, > this does not happen. However, with the K3 powered on and that cable > disconnected, the amp does not key at all, so it is working as expected - but > only with the K3 powered on. Somewhere the K3 is getting its foot in the door > when powered off… > > Jim / K7TXA > > p.s. do you have any idea what Jack was talking about when he said "switch > the RADIO setting of the KPA from K3 to something else, either Serial or > Analog”?? > ______________________________________________________________ > 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 jackbrin...@me.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
