[Elecraft] Possible K3 Line Input Damage

[Bob McGraw K4TAX]

Although in this case as they say,  "the horse is out of the barn, and 
it is too late to close the doors".   This is the main reason, before I 
do any configuration changes, I always make a backup of the 
configuration.   Using the K3 Utility, this is so easy to do. Thus 
taking this extra step has saved my proverbial butt several times.

If you have an earlier configuration saved, then use the utility to 
restore that configuration.

73

Bob, K4TAX

On 3/10/2020 1:08 PM, gt-i at gmx.net wrote:
> Mike,
>
> the input circuit "the fuse" is a transformer (T1) and two resistors 
> (R13, R24). If overdriven, it just goes into saturation and clips the 
> signal, which leads to distortion.  If you have, however, the 
> capability to put seriously more than 1Vpp into it (like 12V?) I don't 
> know what happens.
>
> Another idea: have you checked the setting "MIC SEL" is still on LINE IN?
> I guess you do have acesss to the K3 Serial line, so you could use the 
> K3 Utility to execute macros? Here is mine to switch to LINE IN: 
> "MD2;MN053;UP;UP;MN255;"
> I did had problems with line out in the past, and Elecratf support 
> digged out that it may be an equalizer setting issue for in and out. 
> Try resetting the RX EQ to flat.
> 73 gl Gernot DF5RF
>
> Am 10.03.2020 um 00:50 schrieb 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.................
>>
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