[Elecraft] KX2 / KPA500 (resolved)

[James Bennett]

Let me answer a couple questions here in one message.

Jack - I recall from working with you several years ago on a similar situation that indeed, the amp “defaults” to 60 meters when the K3 is off.

Also, with the interrupter in place, and NO cable between K3 Key Out and amp, the K3 does NOT key the amp. 

So, I now have it working perfectly, as I did when I had a KX3 many moons ago. Here is the setup:

——> KPAK3AUX cable and Key Line Interrupter between K3 and KPA500. Two-way RCA jack splitter plugged into the PA Key on the KPA500; one cable to the K3 Key Out, the other to the KX2 Acc port (ring 2 and shield).

With this configuration, either the K3 or the KX2 can key the KPA500 and drive it as desired.

I see that in the KPA500 manual, Rev D, 3/10/2017, the diagram indicates “Break Key Line to Insert External Equipment”. Interestingly, it also shows the line from the amp going to the K3 Key jack, which I don’t think is correct - it should point to the second jack from the right - the Key Out connection, right?

Jack - do you see any problem in doing the connections as I’ve done? seems to work fine, and I’ve not seen any smoke escaping from either rig!

Jim / W6JHB 

> On Apr 28, 2020, at 5:33 PM, Mark Goldberg <marklgoldberg at gmail.com> wrote:
> 
> My confusion is connecting the KPA500 to both the KX2 and K3 at the same time. I use my KPA500 with two different radios, but it is only connected to one of them at a time. In my case it is:
> 
> RF, RS232 and PTT in from my TS-590S
> OR
> RF, and PTT in from my KX3
> 
> I assumed that pull ups / downs when units are not powered up would mess things up and they are not designed to be wired ored,  especially when not powered up. Since I don't have a K3, I don't know how it connects up.
> 
> 73,
> 
> Mark
> W7MLG
> 
> 
> On Tue, Apr 28, 2020 at 4:48 PM Jack Brindle via Elecraft <elecraft at mailman.qth.net <mailto:elecraft at mailman.qth.net>> wrote:
> I went back and reread this . My question is this - with the interrupter in place, does the K3 still key the amplifier?
> 
> I suspect you are running into the issue of pull-ups on the K3 pulling the PTT signal up to Vcc. Of course Vcc when the K3 is off is 0 volts, which causes the KPA to key.
> We see the same issue with the BAND lines, which is why the KPA500 switches to 60 meters shortly after the K3 is powered off.
> 
> So, I’m wondering what is going on also. More details and tests should resolve the questions.
> 
> 73!
> Jack, W6FB