[Elecraft] K2 - Fuses ...A Cautionary Tale

[Fred Jensen]

In my case, Don is entirely correct, the ground occurred prior to the 
resettable fuse, and the only thing in the path was the trace from the 
power connector through D10 to the AUX 12V pin.  And, believe me, I will 
never "just check to see if it's all OK" again without a fused power 
lead.  It was a stupid mistake on my part, driven by haste ... and I'm 
not sure why, I know better.

Rick has a good point however:  Someone mentioned The Ampere Theorem, 
"Any short circuit will eventually find a fuse."  A corollary is, "Make 
that bigger, it will find something else."  I escaped that this time, 
won't every time unless I pay attention.

I think the bigger lesson for me is, "Pay attention to the details. 
This wouldn't have happened had I not plugged into the wrong connector, 
I *know* the right connector and have done it right many times, I just 
wasn't paying attention.  I still put one hand in my pocket, or sit on 
it, when poking in live gear even though 12V won't electrocute me.  Some 
old habits won't die.  Paying attention seems to have stuttered a bit on 
this one.

Shorts on power leads, inside and outside the radio, can happen. 
Today's batteries have some incredible energy densities and can deliver 
huge currents.  They may not electrocute you but they can sure burn you 
and fry your radio.  Fuse every power lead.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2012 Cal QSO Party 6-7 Oct 2012
- www.cqp.org

On 12/22/2011 5:09 PM, Don Wilhelm wrote:
> Rick,
>
> It is not likely to "break something further down the chain" --
> The K2 has a resettable fuse that will limit the fault current to 5
> amperes or less.  The PC trace that was fried was before the resettable
> fuse.