[Elecraft] KAT 2 Woes

[Don Wilhelm]

Tom,

Yes, that plug offset would have put 12 volts on the VRFDET signal line 
into the KAT2, which would most likely fry U1.

You can avoid that problem in the future by 'keying' the P4 and KAT2 
plug  - remove P4 pin 4 (it is not used) and push a blocking piece of 
wire or toothpick into pin 4 of the plug - carefully put a dab of glue 
on it if the blocking object is loose.  That 'keying' is used for the 
ribbon cable for the KPA100 - so if you are not following my words, 
download that manual and take a look.  With that keying, it is not 
possible to plug it incorrectly.

73,
Don W3FPR

On 8/1/2013 1:09 AM, Tom Field wrote:
> I was reaching the final stages of installing the KAT2 to my K2. When I
> added power, I heard some sizzling and smelled smoke, This didn't happen
> with previous power up testing and the build and testing seemed to go
> without problems. I noticed that U1 was warm.
> Careful inspection showed that when I plugged J8 into the Control Board of
> the k2, I inadvertently shifted the plug up one space, causing the wrong
> signals/voltage to go down the wire. Corrected that and proceeded to test.
> The menu for the ATU appeared without problems and the Ant1/2 cycled on and
> off appropriately. When Checking voltage on U4, during TUNE at 5 , I only
> get 0.3 to 0.4 volts.
> The manual suggests that there is a problem with the build of the SWR
> bridge. Will check that, but my question is did I fry U1 and could that be
> the cause of what I see?
>
>