[Elecraft] Possible K3 Line Input Damage

[Michael Tope]

Recently I've made some configuration changes at my remote station that 
should in the end improve things. In the short term, however, it has 
caused problems when working voice. Specifically I was getting feedback 
if I raised the line out level on the PC too far past a certain 
threshold which seem to depend on the K3 compressor settings (in case 
you are wondering, yes, the K3 monitor level was set to 0). Despite 
these problems, I was able to make some 40 meter SSB contacts Sunday 
morning during the ARRL DX Phone contest.

On Sunday afternoon, I connected to the remote with about ten minutes to 
go in the contest and heard PY0F calling CQ on 20 meters with a very 
loud signal. Not having touched the settings from the night before, I 
figured I would tweak the tuning on the KAT-500 and then just call him. 
Things did not go well. The rig broke into audio feedback and I lost 
transmit/receive control for what seemed like a forever, but was 
probably in reality only about 15 seconds.

After I regained control of the rig, I power cycled the rig and then 
power cycled the computer (I can do that remotely). The K3 still works 
fine on CW, but I can no longer operate SSB. TeamViewer indicates I am 
getting audio to the remote site, but the radio no longer responds. I've 
tried both VOX and manually switching to transmit. Either way, I get 
nothing. I even tried playing a local audio source on the computer at 
the remote site which should have gone straight into the K3. I still got 
nothing.

IS IT POSSIBLE TO DAMAGE THE LINE INPUT OF THE K3 IF IT IS OVERDRIVEN BY 
A SOUNDCARD LINE OUTPUT OR DOES THE K3 SOMEHOW SELF-PROTECT? IF THE 
FORMER, WHAT PART IN THE K3 SERVES AS THE "FUSE"?

I know it is premature to assume the K3 is damaged as I haven't 
physically been to the remote site test the rig since the incident, but 
I wanted to understand what the worst-case scenarios might look like.

Thanks & 73,

Mike W4EF.................