[Elecraft] KX1 died. Where to start?

[Don Wilhelm]

  Oscar,

If your coax switch was connected properly, no harm should have been 
done to the KX1.

OK, now that the MCU chip has been verified as fully seated, you are in 
for some in-depth troubleshooting.
The first thing that should be checked is the DDS frequency - but if you 
do not have a frequency counter, that is difficult.
I assume you do have another HF receiver (the K3 if nothing else) - if 
so, operate the KX1 into a dummy load and couple the other receiver near 
the dummy load with a short antenna - you should hear the KX1 transmit 
quite close to the frequency on the KX1 dial.

If the KX1 transmit frequency is close to the frequency the KX1 is tuned 
to, that part is good, and we can rule out the KX1 MCU and DDS for transmit.

Next, try a "quick and dirty" check of the KX1 receiver - connect the 
center conductor of your antenna (using a jumper wire) to U6 pin 1 - do 
you hear signals as you tune?  If not, you are in for some greater "in 
depth" signal tracing (tell me what equipment you have available) - but 
if you do, then the problem is in the Low Pass Filter of your KX1.

73,
Don W3FPR

On 11/13/2010 8:27 PM, Oscar, WB5GCX wrote:
> Don,
>    Removed and re-seated the MCU.  No change in operation.  Also closely
> inspected for no/bad solder -- all looks good.
>
>    Kept thinking about if I could have done anything to cause this.  I
> remembered I had both the KX1 and my K3 connected via 18" jumpers to a coax
> A/B switch to share my main HF antenna.  Was doing some receiver comparisons
> between the two, and have used this configuration to easily use the KX1
> indoors with the main antenna.  Always before I have always disconnected the
> coax from the KX1 before transmitting with the K3 (as well as moving the A/B
> switch to the K3 position).
>
>    The last time I had the KX1 hooked up this way, I may not have removed the
> coax from the KX1 before using my K3 on 40m cw, and 80m SSB.  I'm not sure I
> tried/used the KX1 after doing this.
>
>    Could strong RF from the K3 maybe have "fried" the KX1 MCU (or other
> component)?  Perhaps the A/B switch isolation is not so good -- or stray RF,
> etc.?
>
> Oscar, WB5GCX